Support `import type`

Many times, developers want to declare an interface next to a function. However, when other files need to utilize that interface, they are currently forced to also bring along the runtime functions with it.

'pkg:/components/Button.bs
interface ButtonBase
    text as string
end interface

sub init()
end sub

'pkg:/components/MainMenu.bs
import type "pkg:/components/Button.bs"

'yay, no "duplicate function named init" diagnostic
sub init()
    button = {} as ButtonBase
end sub

Requirements:

1 ) add a new type keyword to the import statement (i.e. import type "pkg:/source/common.brs")

Implementation details:

• import type will bring along all:
  • interfaces
  • enums
• these script imports are deleted from the xml file at transpile time since they do not represent any runtime code

Future enhancements can be to import classes as types, but there's more work involved with that as we need to flag certain types

Start by tracing how import statements are parsed and how script imports are emitted into the XML during transpilation. Check the existing handling for interfaces and enums, then verify that import type makes those declarations available without runtime imports. Done means type-only imports are removed from the generated XML while ordinary imports retain their current behavior.