Aliases to recipes in submodules

[john-cd]

To "alias" a recipe in a module, I believe one has to call just again:

# Format all bin and lib files
f:
  @just code fmt

# Format all packages and their local path-based dependencies
fa:
  @just code fmtall

Could we have the following?

alias f  := code::fmt 

[casey]

Good suggestion! I added it to #2252.

I think this should be pretty easy to add, so added the good first issue label in case anyone wants to take a crack at it.

[corvusrabus]

Can I grab this one?

[casey]

Sure, go for it! Rough sketch of what I think will be needed:

1. Add a ColonColon token kind, which will be used for path separators
2. Add a Parser::parse_path function, which will parse a colon-separated path of names
3. Change Parser::parse_alias to parse a path
4. During analysis, verify that the path points to a valid recipe, and resolve the alias to that recipe.

4 is probably the trickiest, since this is the first time we've had to deal with inter-module dependencies.