Add a collection filter to the search

[mootari]

Is your feature request related to a problem? Please describe.

Ported from https://observablehq.com/@observablehq/searching-on-observable#comment-1dc4c802bd9a5f7a. See thread for additional context.

The search is missing a filter for collections. At a minimum the filter should take a collection name. If possible there should also be a filter to find or exclude notebooks that have not been assigned to any collection.

Use cases:

• Search through notebooks in a collection, sorting the results by the various criteria available in the search (but absent from collections)
• Review notebooks that have not yet been assigned to a particular collection.
• Treat collections as a tagging system for notebooks, search and filter by various "tags" (inclusive and exclusive).

[CobusT]

I am just relooking at this and realized that @triptych's request in #369 was a bit different from this request. @mootari I think you are asking to be able to search for notebooks in a particular collection (or in no collection). Whereas the other request was to show collections in the search results. I think we should re-open #369 and keep them separate?

[mootari]

@CobusT I agree. It might also help to summarize this distinction in the other issue.

[CobusT]

We now have collection:some-collection as a search parameter! See https://observablehq.com/@observablehq/searching-on-observable#cell-226

[hellonearthis]

can we search for 1 or more hash tags?

[CobusT]

tag search will be available soon!