Improve docs (links, shield, examples)

[FabijanC]

Usage related changes

• Fix broken links (Discord)
• Add Examples section, with a link in the sidebar and the navbar
• Add shields.io badge to README.md
• Closes #478

Development related changes

• To support the Examples navbar link, I had to create versioned_docs/version-0.1.2/examples.md

Checklist:

• [x] Checked out the contribution guidelines
• [x] Applied formatting - ./scripts/format.sh
• [x] No linter errors - ./scripts/clippy_check.sh
• [x] No unused dependencies - ./scripts/check_unused_deps.sh
• [x] No spelling errors - ./scripts/check_spelling.sh
• [x] Performed code self-review
• [x] Rebased to the latest commit of the target branch (or merged it into my branch)
  • Once you make the PR reviewable, please avoid force-pushing
• [x] Updated the docs if needed - ./website/README.md
• [x] Linked the issues resolvable by this PR - linking info
• [x] Updated the tests if needed; all passing - execution info