Update README

[crimist]

• Update firefox EGL conf to mention direct backend.
• Update direct backend grammar and compatibility list.

[elFarto]

The EGL backend being referred to is Firefox's EGL backend, rather than it's GLX one. Firefox can use this driver's EGL or direct backend without issue.

I do agree that description does need rewording as having a second 'EGL backend' is confusing.

[crimist]

Ah I see, I just assumed (and found it true) that the MOZ_X11_EGL didn't need to be set with the direct backend.

Would you be open to some work on the README? I could add a table of contents and clean it up a little.

[elFarto]

It's likely that EGL doesn't need to be forced for recent versions of Firefox, as I believe it's now the default. When the library was initially released that wasn't the case.

I would absolutely be open to the README being worked on.

[crimist]

What is the minimum NVIDIA driver version required for this package? Probably worth mentioning in the installation section to reduce issues like #136.

[crimist]

Nevermind, I see it's 470 or 500+ drivers.

[elFarto]

Thanks, those changes look good!