Feature Request: Support linting of shebang recipes

I like that `just` lets me put a lot of what I would normally write as a mass of shell scripts into a Justfile. But when recipe logic and documentation as code leads me to write a shebang recipe it is not long before I wish I could use a linter to make sure I have not blundered in writing that. Since most of my shebang recipes are using `bash` I personally would like some way to have `just` save a recipe to its temporary file and then, instead of executing it, have it run a locally installed linter like [ShellCheck](https://github.com/koalaman/shellcheck) against that file. Those using other languages would likely need a way to specify their own linters of choice, however.

Implementation-wise, perhaps a new just variable **linter** could be defined as a companion to **shell** to specify the default linter for recipe lines.

As an initial implementation perhaps it would be sufficient to have a `just --lint [recipe]` option that would write the designated recipe's body to the "temporary file" and have `just` simply output the path to that for users to lint manually. That might enable the maximum flexibility for users and other tools that might incorporate `just` capabilities. Or maybe a --linter option would work similarly to --shell to invoke the designated linter on recipe bodies. Another possibility might have `just` recursively call itself to invoke `lint: target:` recipes. Maybe recipe attributes could be extended to cover different shebang languages, i.e.,

[bash]
lint target:
shellcheck {{target}}

[python3]
lint target:
pylint {{target}}

where again, the target path would come from `just`'s temporary path generation. Perhaps `~/.user.justfile ` is a mechanism to leverage to specify user preferences for shell/linter correspondences via a map/associative array or recipe attributes as above.

I could do something with `junk -s [recipe] | tail -n +3 | shellcheck -` but then I have to figure out how to deal with variable substitutions. I'm not a rust developer nor familiar with `just` internals so I'm spit-balling here as a happy `just` user wanting to be happier.

Finally, perhaps this request overlaps somewhat with #1094 Question: Language Server, though that seems to me like a much bigger ask. Thanks for considering it, and for just.

Start by reading how just handles shebang recipes, creates temporary files, performs variable substitution, and parses command-line options. The issue presents several competing designs, including --lint, --linter, and lint recipes, so first narrow the scope to one approach. Done should include a defined linting workflow for recipe bodies, with substitutions handled correctly.

Written by the indexing model from the issue text.