Update contributing.md file to provide better documentation

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## Summary
The contributing.md file is quite long and should probably be split out into separate docs to encourage people to read it more.

## 💬 Description
Each section of the contributing.md file should be split up and linked to from the contributing.md file. Essentially all of the top headings on the table of contents at the start of the contribution guide could be split up.

Coding standards and best practices may want to split out further as it is likely to be a large section after #1229 is implemented.

**Look into github docs to see if there's a nice way to format.**

## Why do we need it?
To encourage contributions following our standards.

Start by reading contributing.md and its table of contents, then review GitHub's documentation guidance for organizing contribution guides. Done means the top-level sections are split into separate linked documents, with coding standards and best practices considered for further separation after #1229.

Written by the indexing model from the issue text.