Improve gsc readability.md

To make it easier and more pleasant to read/write gsc, you can open the files using Visual Studio Code

Then, install the GSC extension by eyza, like that:

And confirm:

Now, when opening gsc files with Visual Stuio Code, to get the text colorized (and enable other features of the extension), you would have to accept this by clicking "Open":

The text should looks nice like that:

If sometimes, the text isn't colorized, you can click on "Restricted Mode" at the bottom left:

Then click "Trust":

Now you can go back to your file tab, the text will be colorized.