Add `*.klint` to `.gitignore`

[JCKeep]

When running klint on the Linux kernel, it produces many intermediate artifacts, such as libkernel.klint. However, we usually don’t care about these intermediate files, so add them to .gitignore.

It's good for the good first issue

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This requires submitting a proper patch to the LKML and the Rust for Linux mailing list. Please recall to test your changes (including generating the documentation if changed, running the Rust doctests if changed, etc.), to use a proper title for the commit, to sign your commit under the Developer's Certificate of Origin and to add a Suggested-by: tag, and a Link: tag to this issue. Please see https://docs.kernel.org/process/submitting-patches.html and https://rust-for-linux.com/contributing for details.

[ojeda]

Cc: @nbdd0121

If Gary plans to keep those files when integrating Klint into the kernel, then it sounds like a good idea. Maybe he already has such a patch, though?

[nbdd0121]

Alternatively I can have klint generate files that are already ignored? E.g. .klint.o or .klint.rmeta

[JCKeep]

Alternatively I can have klint generate files that are already ignored? E.g. .klint.o or .klint.rmeta

Oh, this looks better.

Another thing to note is *.klint-journal. Such as libkernel.klint-journal.