Added a launch script for the editor on Linux

[britzl]

This change adds a launch script for the editor on Linux. The launch script will detect common problems when launching Defold on Linux and either try to automatically fix the problem or suggest a solution to the user.

Fixes #6372

[JustAPotota]

This script's libffi detection won't work for Arch-based distros like Manjaro since they store libraries directly in /usr/lib/ instead of /usr/lib/x86_64-linux-gnu/. It should be fine to just add additional checks for /usr/lib/libffi.so.6 and /usr/lib/libffi.so.7 alongside the Debain paths. It'd also be nice to have different error messages for Arch:

glxinfo could not be found
Install using 'sudo pacman -S mesa-utils'

Defold requires libffi.so.6 or libffi.so.7
Install using 'sudo pacman -S libffi7'

[savegame]

path to libs in script are

/usr/lib/x86_64-linux-gnu/

but in Red Hat based distros like Fedora, they are in

/usr/lib64

[JCash]

I guess we should avoid commented out code, unless there's some documentation explaining it?