Cross check tokens with current mint language for correctness and that they are up to date

[jgarte]

Below is a quote from a conversation I had with Szikszai Gusztáv on the matrix gitter bridge:

Are any of the tokens incomplete or deprecated in any way?

Most of it is good:
operators - https://github.com/mint-lang/mint/blob/master/src/parsers/operation.cr#L5
all tokens should be in here https://github.com/mint-lang/mint/tree/master/src/parsers but there is no specific list
style units, colors are not enforced at all
properties - https://github.com/mint-lang/mint/blob/master/src/assets/css_properties

[jgarte]

These PRs are related to this ticket:

mint-lang/mint#528

mint-lang/mint#503