Update navbar

[andrewnicols]

When I originally wrote the navbar I wanted to keep it fairly minimal and we initially did not have much to add.

Since the first version of the docs we have added:

• release notes
• docs for the Moodle App
• Content guidelines
• Documentation on writing documentation

I feel that all of these things should really be in the navbar.

This commit adds:

• Moodle App
• Releases
• Writing
  • Content guidelines
  • Documentation

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[andrewnicols]

[github-actions]

⚡️ Lighthouse report for the deploy preview of this PR

URL	Performance	Accessibility	Best Practices	SEO	PWA	Report
/	🟠 75	🟢 95	🟢 100	🟢 90	🟢 100	Report
/docs/5.0/apis/commonfiles	🟠 51	🟢 93	🟢 100	🟢 100	🟢 100	Report
/general/development/gettingstarted	🟠 68	🟢 95	🟢 100	🟢 90	🟢 100	Report
/general/releases	🟠 71	🟢 95	🟢 100	🟢 100	🟢 100	Report