[todo] Fix SwiftLint workflow step

[kyzmitch]

Currently it could be triggered by pull request, but for some reason it can't find swift files to check:

• PR Test SwiftLint workflow #63
• https://github.com/kyzmitch/Cotton/actions/runs/5742699631/job/15565371248?pr=63

Run norio-nomura/action-swiftlint@3.2.1
  env:
    DIFF_BASE: master
...
"/home/runner/work/Cotton/Cotton":"/github/workspace" 5bedb4:05ddb88e99204900a5dd037a6155f6a8
fatal: detected dubious ownership in repository at '/github/workspace'
To add an exception for this directory, call:

	git config --global --add safe.directory /github/workspace
error: Could not access 'FETCH_HEAD'
No Swift file changed

[kyzmitch]

it should be better now after merge of PR #66