docs: center header badges & add contributing section

[Pymetheus]

Description

Wraps the README badge area in a centered

for improved alignment and adds a new 'Contributing' section that directs contributors to GitHub Discussions, Issues, and Pull Requests. Also includes minor whitespace/formatting adjustments.

Type of Change

• Bug fix (non-breaking change that fixes an issue)
• New feature (non-breaking change that adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation update
• Code refactoring
• Performance improvement
• Test addition or update

Related Issue

no issue

Changes Made

• Wraps the README badge area in a centered
• Adds a new 'Contributing' section

Testing

Describe how you tested your changes:

• Unit tests pass
• Integration tests pass
• Manual testing performed

Screenshots (if applicable)

Add screenshots to help explain your changes.

Checklist

• My code follows the project's style guidelines
• I have performed a self-review of my code
• I have commented my code, particularly in hard-to-understand areas
• I have updated the documentation accordingly
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes

Additional Context

Add any other context about the PR here.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

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