feat(cli/lint): Add support for reading input from stdin

[magurotuna]

Resolves #7218

Given the following file named file.ts

let a: any;

then we can lint it in two ways:

1. deno lint --unstable file.ts
2. cat file.ts | deno lint --unstable - (new!)

I also added integration tests and updated the doc.

My concerns:

• As I commented to lint_stdin, all inputs from stdin are treated as TypeScript. Should some flag like --ext be added to handle other types? (something like cat file.jsx | deno lint --unstable - --ext=jsx)
• The linter requires file_name so I put it as _stdin.ts for now, referring to

  deno/cli/fmt.rs

  Line 179 in 9bfb0df

  match formatter.format_text(&PathBuf::from("_stdin.ts"), &source) {

  I wonder if there is a preferrable file name.

[bartlomieju]

• As I commented to lint_stdin, all inputs from stdin are treated as TypeScript. Should some flag like --ext be added to handle other types? (something like cat file.jsx | deno lint --unstable - --ext=jsx)

That's okay

The linter requires file_name so I put it as _stdin.ts for now, referring to

That's also okay

[bartlomieju]

LGTM! Thanks @magurotuna, this PR brings us closer to VSCode integration.

[bartlomieju]

Nice tests

[ry]

Since lint is marked unstable, I think we can land this now.