lang: [pl] add Polish translation

[mieszkou]

I added a Polish translation of the texts

[datamweb]

Hi,
Thank you for contributing!
Please see #235 (comment)

[kenjis]

Please fix the following failure.

There was 1 failure:

1) Tests\Language\PolishTranslationTest::testAllIncludedLanguageKeysAreTranslated with data set "pl" ('pl')
Failed asserting that the translated language key "Auth.token" in "pl" locale differs from the original keys in the main repository.
Failed asserting that an array is empty.

/home/runner/work/shield/shield/tests/Language/AbstractTranslationTestCase.php:259

https://github.com/codeigniter4/shield/actions/runs/9068936216/job/24922062972?pr=1117

[kenjis]

Also, please sign all commits.
See https://github.com/codeigniter4/CodeIgniter4/blob/develop/contributing/pull_request.md#signing
https://github.com/codeigniter4/CodeIgniter4/blob/develop/contributing/workflow.md#gpg-signing-old-commits

[datamweb]

@mieszkou thank you!
The last thing to do is to sign all the commits.

It is explained gpg-signing-old-commits.

As a faster alternative, you can still securely sign commits without the -S option in git commit. See Set Default Signing.

[kenjis]

Thank you!

[michalsn]

Nice work!

[datamweb]

@mieszkou Welcome to Shield Contributors!
Merged.