within `asm!` the token "in" highlights like a normal keyword, not like a register specifier.

[Lokathor]

The "in" token should highlight the same as other register specifiers when used inside of asm!

(note: it would also be fine if all register qualifiers and the options entry were highlighted like keywords, as long as it's consistent)

[jonas-schievink]

We don't currently have any semantic highlighting for asm!, so this is just caused by the built-in grammar. cc #6031