Bump reviewdog version to 0.20.1

[SMoraisAnsys]

Hi, I was wondering if this action could use a more recent version of reviewdog.

Currently, the version used is 0.17

vale-action/src/input.ts

Line 61 in 91ac403

const localReviewDog = await installReviewDog("0.17.0", core.getInput('reviewdog_url'));

while the most recent version is currently 0.20.1

One of the gain from changing the version would be to leverage -fail-level instead of -fail-on-error.
I don't know if you are open to the idea of adding back the level input which was removed previously (c4213d4). Since I couldn't find information on why it got removed, maybe that one of the reason for such limitation was the lack of feature in reviewdog and using the new version might help on this.

More information:

• -fail-level impact on exit code
• -fail-on-error deprecation

[jdkato]

Yes, I'll update when I get a chance (PRs are also welcome).

You can also currently change the version of reviewdog by providing a value for reviewdog_url, although this won't help in cases where new features aren't yet supported in this action.

[SMoraisAnsys]

Cool, I'll give it a try then ! Thanks for confirming that you are not against this changes :)

[anaxite]

I'm having a go at this request, and would appreciate feedback on the PR when possible.

Does it make sense to re-add the level input at the same time, or do it later? I'm leaving the PR as draft until I'm sure.