docs: Add sections for missing blockTypes

[Lehmanator]

Add sections to "Builtin Block Types" for each blockType without one.

Fixes: #386 (partially)

• Matches existing sections by inserting the contents of the file with the blockType definition.
• Fixes typo in comment in blockTypes.nvfetcher definition file.

If desired, I'd also like to:

• Alphabetize the blockType sections (or order according to another scheme)
• Remove the comment strings from the blockType definition files and add them to the documentation.
• Create example definition files for each blockType and add them to the docs.

I could do this in another PR if out of scope for this one.

[blaggacao]

Alphabetize the blockType sections (or order according to another scheme)

👍

Remove the comment strings from the blockType definition files and add them to the documentation.

👎 There are indeed folks for whom the documentation is secondary, think of workflows using lsp "jump to definition", even if not currently possible with nix, approximatable with rg/grep

Create example definition files for each blockType and add them to the docs.

👍 💯