added `.gitattributes` and normalized files by firewave · Pull Request #4668 · cppcheck-opensource/cppcheck

This is just good practice. But it also fixes issues with running .sh files when using a repo checking out on Windows within WSL as well as unexpected EOL changes in Visual Studio-related files as seen in #4652.

No files are changed. By checking Hide whitespaces under the gear when viewing the changes you can see that just .gitattributes was added.

I also added some common extensions we are not (yet) using in the repo like .ps1 and .pdf.