Fix typo in pre-commit config in README

[f-hollow]

First of all, thank you for this very useful tool!

I ran into an issue while trying to add lychee to the pre-commit hook. Here is the account of the steps that I took.

1. I copied the following pre-commit config code from the README into my project's .pre-commit-config.yaml:

   # .pre-commit-config.yaml
   repos:
     - repo: https://github.com/lycheeverse/lychee.git
       rev: 0.15.1
       hooks:
         - id: lychee
           # Optionally include additional CLI arguments
           args: ["--no-progress", "--exclude", "file://"]

2. While committing files, pre-commit returned this:

   An unexpected error has occurred: CalledProcessError: command: ('/usr/lib/git-core/git', 'checkout', '0.15.1')
   return code: 1
   stdout: (none)
   stderr:
       error: pathspec '0.15.1' did not match any file(s) known to git
   Check the log at ...

3. Updating the line rev: 0.15.1 to rev: v0.15.1 fixed the issue.

Hence, this PR is offered to fix the typo in the provided pre-commit config.

[f-hollow]

Not sure why certain CI jobs failed. Please let me know if the issues are related to my changes.

[dscho]

I was as puzzled as you in my PR. Turns out that outside changes (a clippy update?) require fixes such as the ones I proposed in #1423.

[f-hollow]

That's a bit too deep for me.

In this case, should this PR wait till you merge the PRs in question and then do a rebase? Or what would you suggest we do?

[dscho]

@f-hollow I am only a contributor, not a maintainer, so I don't know.

[mre]

@dscho fixed it, so this branch can be rebased. (Thanks @dscho.)
I'm guessing it's because of the recent Rust 1.78 release, which activated some more clippy lints.

[mre]

Oh, and for some context as to why this is broken, it's because of the changes in lycheeverse/lychee-action#204. We forgot to update the lychee docs. Thanks for fixing.

Checked the change again, and it's unrelated to the linked PR.
I think it's always been broken, actually? Either way, glad it's fixed.

Will merge, as rebase won't change much anyway, because we don't have a test for this.

[f-hollow]

@dscho Oh, I assumed by default that your were a maintainer. Sorry!

@mre Thank you for merging my PR!