Prepare for Possible no_std Support

[bushrat011899]

Objective

With Bevy 0.16, there is the possibility of many crates gaining no_std support. Further, no_std support is desirable for crates that will be upstreamed.

Solution

• Added lints to reduce reliance on std.
• Switched to core::prelude instead of std::prelude using #![no_std].
• Added std and alloc as external crates.
• Disabled default features on serde and re-enabled features used directly by this crate.

---

Notes

Once Bevy 0.16 releases, no_std support should be as simple as:

• Adding an std feature and including it in default
• Gating the extern crate std; statement
• Gating the ui_priority and egui_priority features on std
• Potentially adding other support features such as libm, critical-section, and web for ease of use.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 85.74%. Comparing base (d6bcaa3) to head (f27535d).
Report is 1 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master      #52   +/-   ##
=======================================
  Coverage   85.74%   85.74%           
=======================================
  Files          31       31           
  Lines         996      996           
=======================================
  Hits          854      854           
  Misses        142      142           

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[Shatur]

That was quick 😅
Thanks!

No sure why cargo check started to fail, but I don't think it's related to the changes.

[bushrat011899]

I've been getting fast at this! Plus this crate was already very close to no_std compatible anyway