doc: add first development guide

[tixxdz]

Tetragon Open Source project was just released and it does not include
default contributing guidelines.

This patch fixes this by adding:

1. CONTRIBUTING.md file in the root directory as suggested by github documentation:
   https://docs.github.com/en/communities/setting-up-your-project-for-healthy-contributions/setting-guidelines-for-repository-contributors

2. Development guide under docs directory with a section on how to submit pull requests.

3. Moves the DEVELOP.md file from root directory to the docs/contributing/development/ one.

Fixes: #33

Signed-off-by: Djalal Harouni [email protected]

[willfindlay]

WDYT about folding DEVELOP.md into here as a flat section? I'd rather not have it buried behind two clicks.

[tixxdz]

@willfindlay sure, done.

[michi-covalent]

regarding the file location: https://docs.github.com/en/communities/setting-up-your-project-for-healthy-contributions/setting-guidelines-for-repository-contributors

To help your project contributors do good work, you can add a file with contribution guidelines to your project repository's root, docs, or .github folder.

i vote for putting CONTRIBUTING.md at the root directory to be consistent with cilium https://github.com/cilium/cilium/blob/master/CONTRIBUTING.md

[willfindlay]

i vote for putting CONTRIBUTING.md at the root directory to be consistent with cilium https://github.com/cilium/cilium/blob/master/CONTRIBUTING.md

+1, this is also consistent with how many projects do it.

[tixxdz]

@michi-covalent @willfindlay done, hope I did get it all.

[willfindlay]

Looks great