Add script to create icns files. (#7456)
Add script to create icns files. (#7456)

Add script to generate macOS icon file. It does not attempt to integrate with the current build process as the macOS icon file is mostly static.

`libsvg` was chosen because of its low dependency count over other solutions that use backends like Chromium, PhontomJS, etc. ImageMagick's `convert` was tested but resulting PNGs where not satisfactory and would have required an overcomplicated script having to calculate the `density` argument.

* Has a dependency on librsvg (can be installed via Brew)
* Uses SVG file as input
* Can be integrated in later to build process if desired

Closes #7455
JamesWTruher/PowerShell-1,daxian-dbw/PowerShell,TravisEz13/PowerShell,daxian-dbw/PowerShell,PaulHigin/PowerShell,PaulHigin/PowerShell,daxian-dbw/PowerShell,TravisEz13/PowerShell,JamesWTruher/PowerShell-1,JamesWTruher/PowerShell-1,TravisEz13/PowerShell,PaulHigin/PowerShell,daxian-dbw/PowerShell,TravisEz13/PowerShell,JamesWTruher/PowerShell-1,PaulHigin/PowerShell