docs: Update docs structure and add contribution docs.

[coveralls]

Pull Request Test Coverage Report for Build 5214119225

Warning: This coverage report may be inaccurate.

We've detected an issue with your CI configuration that might affect the accuracy of this pull request's coverage report. To ensure accuracy in future PRs, please see these guidelines. A quick fix for this PR: rebase it; your next report should be accurate.

• 4 of 4 (100.0%) changed or added relevant lines in 2 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.002%) to 96.809%

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Totals
Change from base Build 5193321433:	0.002%
Covered Lines:	2267
Relevant Lines:	2334

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💛 - Coveralls