[Merged by Bors] - Comprehensive CONTRIBUTING.md

.gitattributes

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+# From: https://docs.github.com/en/github/getting-started-with-github/configuring-git-to-handle-line-endings
+# Set the default behavior, in case people don't have core.autocrlf set.
+* text=auto
+
+# Explicitly declare text files you want to always be normalized and converted
+# to native line endings on checkout.
+*.rs text eof=lf
+*.toml text eof=lf
+*.frag text
+*.vert text
+
+# Declare files that will always have CRLF line endings on checkout.
+*.sln text eol=crlf
+
+# Denote all files that are truly binary and should not be modified.
+*.png binary
+*.jpg binary
+*.ttf binary

.github/contributing/engine_style_guide.md

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+# Style guide: Engine
+
+For more advice on contributing to the engine, see the [relevant section](../../CONTRIBUTING.md#Contributing-your-own-ideas) of CONTRIBUTING.md.
+
+1. Prefer granular imports over glob imports of `bevy::prelude::*` and `bevy::sub_crate::*`.
+2. Use a consistent comment style:
+   1. `///` doc comments belong above `#[derive(Trait)]` invocations.
+   2. `//` comments should generally go above the line in question, rather than in-line.
+   3. Avoid `/* */` block comments, even when writing long comments.
+   4. Use \`variable_name\` code blocks in comments to signify that you're referring to specific types and variables.
+   5. Start comments with capital letters. End them with a period if they are sentence-like.
+3. Use comments to organize long and complex stretches of code that can't sensibly be refactored into separate functions.

.github/contributing/example_style_guide.md

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+# Style guide: Examples
+
+For more advice on writing examples, see the [relevant section](../../CONTRIBUTING.md#writing-examples) of CONTRIBUTING.md.
+
+## Organization
+
+1. Examples should live in an appropriate subfolder of `/examples`.
+2. Examples should be a single file if possible.
+3. Assets live in `./assets`. Try to avoid adding new assets unless strictly necessary to keep the repo small. Don't add "large" asset files.
+4. Each example should try to follow this order:
+   1. Imports
+   2. A `fn main()` block
+   3. Example logic
+   4. \[Optional\] Tests
+5. Try to structure app / plugin construction in the same fashion as the actual code.
+
+## Stylistic preferences
+
+1. Use simple, descriptive variable names.
+   1. Avoid names like `MyComponent` in favor of more descriptive terms like `Events`.
+   2. Prefer single letter differentiators like `EventsA` and `EventsB` to nonsense words like `EventsFoo` and `EventsBar`.
+   3. Avoid repeating the type of variables in their name where possible. For example, `Color` should be preferred to `ColorComponent`.
+2. Prefer glob imports of `bevy::prelude::*` and `bevy::sub_crate::*` over granular imports (for terseness).
+3. Use a consistent comment style:
+   1. `///` doc comments belong above `#[derive(Trait)]` invocations.
+   2. `//` comments should generally go above the line in question, rather than in-line.
+   3. Avoid `/* */` block comments, even when writing long comments.
+   4. Use \`variable_name\` code blocks in comments to signify that you're referring to specific types and variables.
+   5. Start comments with capital letters; end them with a period if they are sentence-like.
+4. Use comments to organize long and complex stretches of code that can't sensibly be refactored into separate functions.
+5. Avoid making variables `pub` unless it is needed for your example.
+
+## Code conventions
+
+1. Refactor configurable values ("magic numbers") out into constants with clear names.
+2. Prefer `for` loops over `.for_each`. The latter is faster (for now), but it is less clear for beginners, less idiomatic, and less flexible.
+3. Use `.single` and `.single_mut` where appropriate.
+4. In Queries, prefer `With<T>` filters over actually fetching unused data with `&T`.
+5. Prefer disjoint queries using `With` and `Without` over query sets when you need more than one query in a single system.
+6. Prefer structs with named fields over tuple structs except in the case of single-field wrapper types.
+7. Use enum-labels over string-labels for system / stage / etc. labels.
+
+## "Feature" examples
+
+These examples demonstrate the usage of specific engine features in clear, minimal ways.
+
+1. Focus on demonstrating exactly one feature in an example
+2. Try to keep your names divorced from the context of a specific game, and focused on the feature you are demonstrating.
+3. Where they exist, show good alternative approaches to accomplish the same task and explain why you may prefer one over the other.
+4. Examples should have a visible effect when run, either in the command line or a graphical window.
+
+## "Game" examples
+
+These examples show how to build simple games in Bevy in a cohesive way.
+
+1. Each of these examples lives in the [/examples/games] folder.
+2. Aim for minimum but viable status: the game should be playable and not obviously buggy but does not need to be polished, featureful, or terribly fun.
+3. Focus on code quality and demonstrating good, extensible patterns for users.
+   1. Make good use of enums and states to organize your game logic.
+   2. Keep components as small as possible but no smaller: all of the data on a component should generally be accessed at once.
+   3. Keep systems small: they should have a clear single purpose.
+   4. Avoid duplicating logic across similar entities whenever possible by sharing systems and components.
+4. Use `///` doc comments to explain what each function / struct does as if the example were part of a polished production codebase.
+5. Arrange your code into modules within the same file to allow for simple code folding / organization.