Sigificantly improve linux guide

list of changes:

• i've added a list of tested distros to the top of the guide and moved the immutable distro warning
• i've made the lutris and heroic sections of the guide more precise and easier to understand
• added an extra note related to webserver not being started and made the OpenGL note a hair more precise

in general, this guide is a lot easier to understand for most people to understand with my changes, i've even added commands the reader can run to quickly add execution permissions