IsItCicada considers MessageId and Charset (and possibly future) headers to be invalid

[crashdemons]

while isistcicada verifies a select few headers we usually see in an attempt to stem possible gamejacking attempts, it mistakenly excludes other valid headers that are defined in standard (but we generally don't see in-game).

While OpenPGP.JS supports this, the pre-validation steps IsItCicada does (as an attempt to add more warnings than OpenPGP and GPG do) overzealously excludes this - as in the previous ticket also.