[docs] update catalogd web api docs to include metas endpoint

[grokspawn]

tutorials and demos do not include metas , for e.g.

• https://operator-framework.github.io/operator-controller/tutorials/explore-available-content/
• https://operator-framework.github.io/operator-controller/api-reference/catalogd-webserver/
• https://operator-framework.github.io/operator-controller/howto/catalog-queries/

It would also be nice if we could de-dupe content in these, making them more cross-referential instead.