Docs: make information on skipping/cancelling builds more discoverable

[agjohnson]

While linking a user to our docs on skipping builds, I found a gap in our search. I think the issue is mostly terminology though. In documentation we call this cancelling but in the application we refer to this as both skipped and cancelled:

https://beta.readthedocs.org/projects/test-builds/builds/23877501/

But, the content I was looking for was:

• https://docs.readthedocs.io/en/stable/builds.html#cancelling-builds
• https://docs.readthedocs.io/en/stable/build-customization.html#cancel-build-based-on-a-condition

I used the search query skip and had no relevant hits. The queries skip build and skipping build do give the above results back in 3rd and 4th position. The query cancel has direct hits.

Perhaps we need to consolidate terminology in the application/docs here. I think we might be able to just add some hits for skip to our content too, so both queries have hits.

The user here had similar trouble finding this information and was looking on our configuration reference page:

• Allow building frequency to reduce RTD loads #11273 (comment)