[Installation] Minor correction in a sentence

The installation page has the following line which reads (point 5 under the sub-section: Installing for GNU/Linux) -

"You'll need to tell your GNU/Linux that you want the ability to execute shell scripts from the graphical interface....."

1. It should either be "GNU/Linux operating system" or maybe "GNU/Linux distribution"
2. Since we are talking about launching the start-tor-browser.desktop via command line in point 6, we may also direct the user on how to make the file executable via terminal i.e chmod +x start-tor-browser.desktop.