Updated Contributor Guide and added Core Contributors

[ravilach]

Description

Please include a summary of the change and which issue is fixed. Please also include relevant motivation and context. List any dependencies that are required for this change.

Fixes # (issue)

Docs'o'plenty!

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Chore (documentation addition or typo, file relocation)

Testing

• New tests were added with this PR that prove my fix is effective or that my feature works (describe below this bullet)
• This change requires no testing (i.e. documentation update)

Documentation

• All added public packages, funcs, and types have been documented with doc comments
• I have commented my code, particularly in hard-to-understand areas

Final Checklist:

• I followed standard GitHub flow guidelines
• I have performed a self-review of my own code
• My changes generate no new warnings

Additional Information (omit if empty)

Please include anything else relevant to this PR that may be useful to know.