(maint) Clean up comments for Resource::Type
(#21881) Add YARD docs for the format used by Puppet::Resource::Type
(#21881) Validate ResourceType against a json schema in tests
(#21881) Add documentation for Puppet::Indirection::ResourceType::Parser

This clarifies the use of this indirection somewhat and conforms better to
YARD syntax.
(doc) Add other markdown files to YARD
(#21881) Add API docs to YARD

This adds an api_docs directory with static markdown files which get included
in YARD output. The first thing documented is the resource_type http endpoint.
(#21881) Add error responses to resource_type http api

Adds responses seen for general cases of bad request or resource not
found when using the http api for resource_type.
(21881) Adds explantory text and fixes for YARD

From Nick Fagerlund:

Add explanatory text; modify the manifest to not throw an error. Add
node definitions.

Rename files (and any references to them).

Use indented code blocks instead of fenced ones

Our docs toolchain can't handle fenced code blocks yet, and we're going to need
to put this content in multiple places, so it must use least-common-denominator
markdown syntax.

Anchor links are not reliable in YARD

...so we should avoid them and describe anchor positions with English.
Merge pull request #1803 from jpartlow/issue/21881-document-resource-type

(#21881) document resource type