feat(rss): add support for extra protocols via `elfeed-protocol` #1152

Job	Run time
ci-macos (29.2, false)	4m 55s
ci-macos (29.3, false)	4m 40s
ci-macos (release-snapshot, false)	4m 21s
ci-macos (snapshot, true)	4m 21s
	18m 17s

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