Move the list of extensions to the extention-types article

[iOvergaard]

📋 Description

This pull request moves the list of extensions (a table) from the umbraco-package article to the extention-types/overview article. This allows people to see the full list before diving into details in the subarticles. Not all of the extension types have their own article, so it is essential to document them at least a little bit somewhere. If they then later get their own article, you add that link to the table.

I have also added a missing extension type (fileUploadPreview).

📎 Related Issues (if applicable)

N/A

✅ Contributor Checklist

I've followed the Umbraco Documentation Style Guide and can confirm that:

• Code blocks are correctly formatted.
• Sentences are short and clear (preferably under 25 words).
• Passive voice and first-person language (“we”, “I”) are avoided.
• Relevant pages are linked.
• All links work and point to the correct resources.
• Screenshots or diagrams are included if useful.
• Any code examples or instructions have been tested.
• Typos, broken links, and broken images are fixed.

Product & Version (if relevant)

Umbraco 16

Deadline (if relevant)

ASAP

📚 Helpful Resources

• 🧾 Umbraco Contribution Guidelines
• ✍️ Umbraco Documentation Style Guide

[github-actions]

The Link Checker found broken links in your PR.
Please review the following list:

Broken links found in: 16/umbraco-cms/customizing/extending-overview/extension-types/README.md

⚓ Anchor not found → 16/umbraco-cms/customizing/extending-overview/extension-types/foundation/localization.md | Cannot find file

⚓ Anchor not found → 16/umbraco-cms/customizing/extending-overview/extension-types/foundation/repositories.md | Cannot find file

⚓ Anchor not found → 16/umbraco-cms/customizing/extending-overview/extension-types/property-editors | Cannot find file

⚓ Anchor not found → 16/umbraco-cms/customizing/extending-overview/extension-types/workspaces.md | Cannot find file

⚓ Anchor not found → 16/umbraco-cms/customizing/extending-overview/fundamentals/backoffice/property-editors/built-in-umbraco-property-editors/markdown-editor.md | Cannot find file

⚓ Anchor not found → 16/umbraco-cms/customizing/extending-overview/fundamentals/backoffice/property-editors/built-in-umbraco-property-editors/rich-text-editor | Cannot find file

⚓ Anchor not found → 16/umbraco-cms/customizing/extending-overview/reference/configuration/healthchecks.md | Cannot find file

⚓ Anchor not found → 16/umbraco-cms/customizing/extending-overview/reference/security/external-login-providers.md | Cannot find file

⚓ Anchor not found → 16/umbraco-cms/customizing/extending-overview/reference/security/two-factor-authentication.md | Cannot find file

⚓ Anchor not found → 16/umbraco-cms/customizing/extending-overview/reference/umbraco-flavored-markdown.md | Cannot find fileFull Github Actions output