dependency checker got removed long ago.
Add further files to export-ignore. This prevents those files from
distribution when installed via composer or downloaded as zip.
Use .gitattributes to tell git what to ignore during exports.
This will prevent GitHub from adding those files to an archive.
Composer will use the GitHub archive as distribution while downloading.
This prevents none necessary files on production systems. This also
reduces file size of archive and should save disk space and other
resources.
