feat: Extracting the type for arguments to arb files

[ghost]

Some 3rd party modules (like for example phrase) require arb files to contain proper type names for placeholders to be able to generate code correctly. Currently when arb files are extracted from code using extract_to_arb the type is missing for placeholders and therefore code generation for the 3rd party modules generate code that doesn't compile properly.

This PR addresses it by adding the type information to MainMessage and exposing it to the generated arb file in toARB.

[robyf]

I left the company where I was working and took over this on my private github account, that's why it's now reported as sent by "ghost" :)