Documentation of Install Prerequisites for rocqide in Linux (Mint)

[jamesodonnell8762]

README_Linux.md#installation-by-compiling-from-sources-using-scripts--opam could be improved if it stated that if rocqide is to be built then that requires libgtk3 and libgtksourceview-3.0 to have been installed.

I did this with

sudo apt install libgtk-3-dev
sudo apt install libgtksourceview-3.0-dev

I guess (but but have not tested) that

sudo apt install libgtk-3-bin
sudo apt install libgtksourceview-3.0-1

would have been sufficient.