Encode + in WebUI commands so it doesn't get lost #856

Job	Run time
tests (ubuntu-latest, tests)	35s
build (ubuntu-latest, noradio)	1m 56s
tests (macos-latest, tests)	45s
build (ubuntu-latest, wifi)	2m 28s
tests (windows-latest, tests_nosan)	1m 22s
build (ubuntu-latest, bt)	2m 16s
build (macos-latest, noradio)	1m 30s
build (macos-latest, wifi)	1m 45s
build (macos-latest, bt)	1m 38s
build (windows-latest, noradio)	4m 25s
build (windows-latest, wifi)	5m 23s
build (windows-latest, bt)	4m 11s
	28m 14s

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