* Create simple CLI tool to get the filename from a brandname
https://github.com/simple-icons/simple-icons/pull/2589#issuecomment-585902427
* Update contributing guidelines on new SVGs' filenames
* Fix incorrect filename in package.json script
* Add file header to get-filename script
* Update contributing guidelines' section on SVG filenames
Co-Authored-By: YoussefRaafatNasry <youssefraafatnasry@gmail.com>
