chore: add .gitattributes file

(cherry picked from commit f310f6a6)

Co-authored-by: Jan Wennrich <jan.wennrich@pcsg.de>

.gitattributes

+
+# Ignore developer files when exporting
+.gitattributes         export-ignore
+.gitignore             export-ignore
+.gitlab-ci.yml         export-ignore
+.phive                 export-ignore
+captainhook.json       export-ignore
+phpcs.xml.dist         export-ignore
+phpstan-baseline.neon  export-ignore
+phpstan.dist.neon      export-ignore
+phpunit.dist.xml       export-ignore
+tests                  export-ignore
+
+# Explicitly set file type and line endings for PHP files, improves git diff output
+*.php     text eol=lf diff=php
\ No newline at end of file

.gitignore

+
+tools/