grammar: consider adding support for hashbang scripting

[lucab]

This is a new-feature request for Quint grammar.

I recently added an example which contains this human-readable comment:

quint/examples/classic/distributed/TeachingConcurrency/teachingConcurrency.qnt

Lines 6 to 7 in 75eac36

	* Run in verifier with:
	* quint verify --temporal correct teachingConcurrency.qnt

However, on Unix systems I'd like to be able to directly run this model as ./teachingConcurrency.qnt, by adding a starting hashbang line like the following:

#!/usr/bin/env -S quint verify --temporal correct

This is not currently possible because the starting # is not a valid token:

./teachingConcurrency.qnt:1:1 - error: [QNT000] token recognition error at: '#'
1: #!/usr/bin/env -S quint verify --temporal correct
   ^

./teachingConcurrency.qnt:1:2 - error: [QNT000] token recognition error at: '!/'
1: #!/usr/bin/env -S quint verify --temporal correct
    ^

./teachingConcurrency.qnt:1:4 - error: [QNT000] mismatched input 'usr' expecting {'module', DOCCOMMENT}
1: #!/usr/bin/env -S quint verify --temporal correct
      ^^^

error: parsing failed

For reference, Javascript was in a similar situation and recently added hashbang support in ES14 (in 2023):
https://www.w3schools.io/javascript/shebang-examples/

I think there are two alternative ways to implement this:

1. Adding a new token rule for # as another starting marker for single-line comments (similar to // and ///), anywhere in a file.
2. Adding a custom token rule for #! as a new starting marker for an hashbang line, only valid at the beginning of a file.

[bugarela]

Oh, I didn't know we could use commands like this in the hasbang! This is awesome. Thanks for reporting, this should be easy to implement as you suggest :)