Add none reporter and option to hide file header for better in editor support

[rrothenberger]

Hey 👋

The goal of this PR is to make it easier to use this great tool within editors, for example using it with conform. It does that by adding a new reporter: none, which will prevent reporting any linter output to stdout, and by adding flag --no-file-header which will prevent outputting this line:

================ /path/to/file.html.erb ==================

Naming is hard, so more than happy to adjust naming.

Example:

There is another PR with similar changes: #357, the main differences are:

• none reporter just does not output anything instead of moving the lining logs into stderr, as I was afraid it might still be read by some editors.
• I didn't want to change behavior of all cli outputs by setting --format - personally wouldn't expect that from the CLI, so instead I decided to add new flag that disabled the file header from above.

I skipped specs for the reporter itself, as this just prevents outputs.

---

If someone found this out looking for solution for conform - even if this is not merged, you still can use erb_lint with conform, just not through stdin, example configuration:

    formatters = {
      erb_lint = {
        stdin = false,
        tmpfile_format = ".conform.$RANDOM.$FILENAME",
        command = "bundle",
        args = { "exec", "erblint", "--autocorrect", "$FILENAME" },
      },
    },

[shetty-tejas]

Rather than introducing a new option, can we just assume that when the 'none' reporter is being used, we ignore the header?

[etiennebarrie]

Can you check whether #393 would work for you? I think it should.