Encode + in WebUI commands so it doesn't get lost #864

Job	Run time
tests (ubuntu-latest, tests)	29s
build (ubuntu-latest, noradio)	2m 3s
tests (macos-latest, tests)	57s
build (ubuntu-latest, wifi)	2m 24s
tests (windows-latest, tests_nosan)	1m 19s
build (ubuntu-latest, bt)	2m 6s
build (macos-latest, noradio)	1m 47s
build (macos-latest, wifi)	2m 34s
build (macos-latest, bt)	2m 7s
build (windows-latest, noradio)	4m 31s
build (windows-latest, wifi)	4m 37s
build (windows-latest, bt)	5m 32s
	30m 26s

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