Added instructions for installing EPEL and RPM Fusion.

[rl2939]

What does this pull request do?

This pull request adds instructions for adding the EPEL and RPM Fusion software repositories, with GPG key verification.

Why?

This pull request aims to make the process of installing several software repositories more clear for the end user.

The current documentation does not explain how to install EPEL in a clear manner (see https://github.com/AlmaLinux/wiki/issues/232). This pull request changes the instructions to the official quickstart guide on the Fedora project website.

In addition, there are no instructions on how to install RPMfusion (which provides additional packages) anywhere on the website. The RPMfusion website does have directions on how to install their repositories, but does not do it in a way where the user can verify the GPG signing key in an easy manner. This pull request adds instructions on how to install RPM Fusion as well as verifying the signing keys.

Also included is an guide on how to install both EPEL and RPM Fusion. This is at the bottom of the documentation section so that new users can find it.

fixes https://github.com/AlmaLinux/wiki/issues/232

[bennyvasquez]

@xsub @rl2939 it's not clear to me, so I wanted to check. Was this content in this PR included as part of #265?

[rl2939]

I believe the PR was reverted (not included). @xsub Is there anything that needs to be corrected in this PR?

[xsub]

Hi @rl2939!

I initially cherry-picked your commit and then attempted to enhance it, which unfortunately led to some confusion with versions during the merge. That's why my commit is missing it – my apologies 😅

Regarding the enhancements:

• I completely get your idea to rename "system series" to "post installation." However, I've decided to skip that for now. This is partly because the After-Installation Guide by @sboldyreva was recently added, which includes "enable-necessary-repositories." Your content could easily link to this guide...

• Considering the above, I was thinking maybe we could move your instructions to a dedicated "System Series" how-to?

I’d really value your thoughts on this, @rl2939, and @bennyvasquez, I’d also appreciate your input. Your insights would be very helpful in defining our approach 😊