Encode + in WebUI commands so it doesn't get lost #860

Job	Run time
tests (ubuntu-latest, tests)	47s
build (ubuntu-latest, noradio)	2m 7s
tests (macos-latest, tests)	36s
build (ubuntu-latest, wifi)	2m 17s
tests (windows-latest, tests_nosan)	1m 20s
build (ubuntu-latest, bt)	2m 14s
build (macos-latest, noradio)	2m 40s
build (macos-latest, wifi)	2m 15s
build (macos-latest, bt)	1m 37s
build (windows-latest, noradio)	4m 29s
build (windows-latest, wifi)	5m 12s
build (windows-latest, bt)	5m 53s
	31m 27s

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