[Bug] Unsound hack in JA4 c-part

[XOR-op]

TrackMe/ja4.go

Lines 82 to 85 in d9579a8

	// VERY dirty hack: append padding, because it gets filtered out for JA3
	// but we want it here. _SHOULD_ be included in ever TLS clienthello, so
	// _shouldnt_ cause any issues.
	extensions = append(extensions, "21")

is under an unsound assumption that every TLS clienthello will include a padding extension. I don't see any standard that requires padding extension as a mandatory component. In fact, some implementations, e.g. curl on my machine, do NOT have padding in the extensions.