Support `align` directive

[DonaldHays]

https://rgbds.gbdev.io/docs/v0.8.0/rgbasm.5#Requesting_alignment

While ALIGN as presented in SECTIONS is often useful as-is, sometimes you instead want a particular piece of data (or code) in the middle of the section to be aligned. This is made easier through the use of mid-section ALIGN align, offset. It will alter the section's attributes to ensure that the location the ALIGN directive is at, has its align lower bits equal to offset.

This might not require anything more than adding the align keyword in directive IntelliSense contexts.