Docs: Documentation updates

[isabelle-dr]

Summary:

This PR contains various updates to the documentation.
It replaces PR #1234 and #1252
It closes issues #1175, #1225, #1150, #1178
Overview:

• added two images showing the PR process and a decision tree "what to do with the acceptance test result" in CONTRIBUTING.md so that contributors know what to expect
• created new issue templates, using GitHub forms, and a link to the slack channel in the "new issue" page
• a few aesthetic changes in README.md
• typos in README.md and RULES.md
• updated RELEASE.md with naming the artefacts and added the new step in the wiki

Expected behavior:

An improved documentation, better issue templates

Please make sure these boxes are checked before submitting your pull request - thanks!

• [ ] Run the unit tests with gradle test to make sure you didn't break anything
• Format the title like "feat: [new feature short description]". The title must follow the Conventional Commit Specification(https://www.conventionalcommits.org/en/v1.0.0/).
• Linked all relevant issues
• [ ] Include screenshot(s) showing how this pull request works and fixes the issue(s)

[emmambd]

This looks great @isabelle-dr! I had 2 minor comments.

[bdferris-v2]

Small nits aside, LGTM

[isabelle-dr]

Thanks for the comments Brian and Emma 🙏.
Merging this PR