feat: Add "deno ast" subcommand

[littledivy]

Leverages the swc ast parser utility behind the --unstable flag

Closes #2355

[bartlomieju]

Code looks good 👍

@divy-work please add an integration test that checks the output of produced AST (just a small script will be enough).

@ry what do you think about this feat? We can leave it behind --unstable time for some time.

[littledivy]

Sure will do. I think if future we can add an option to write the output json to a file.

[n10000k]

I think we need the --unstable to show that the output currently isn't stable, which I think @ry was getting at?

[littledivy]

I think we need the --unstable to show that the output currently isn't stable, which I think @ry was getting at?

Yes, it is currently behind --unstable but the output is quite stable and also has strong typings available.
See https://github.com/swc-project/swc/blob/master/node-swc/src/types.ts

[littledivy]

Hope the tests work now lol. (2 hours wasted)

EDIT: it was a newline issue 🤦

[CLAassistant]

All committers have signed the CLA.

[bartlomieju]

@littledivy thank you for the PR, but after all I think this functionality should be implemented by third party libraries (#2355 (comment))