Mention community-maintained themes #1012

Job	Run time
lint	18s
ruby-versions / Generate Ruby versions	3s
test (3.0, ubuntu-latest)	27s
test (3.0, macos-latest)	30s
test (3.0, windows-latest)	1m 12s
test (3.1, ubuntu-latest)	29s
test (3.1, macos-latest)	24s
test (3.1, windows-latest)	1m 20s
test (3.2, ubuntu-latest)	30s
test (3.2, macos-latest)	32s
test (3.2, windows-latest)	2m 2s
test (3.3, ubuntu-latest)	24s
test (3.3, macos-latest)	28s
test (3.3, windows-latest)	2m 47s
test (head, ubuntu-latest)	31s
test (head, macos-latest)	22s
test (head, windows-latest)	1m 15s
test (jruby, ubuntu-latest)	2m 2s
test (jruby, macos-latest)	1m 37s
test (jruby-head, ubuntu-latest)	2m 7s
test (jruby-head, macos-latest)	1m 47s
test (truffleruby, ubuntu-latest)	2m 18s
test (truffleruby, macos-latest)	1m 50s
test (truffleruby-head, ubuntu-latest)	3m 20s
test (truffleruby-head, macos-latest)	2m 31s
	31m 6s

Provide feedback