Added info for Rounded i3-gaps to README

[bpetterborg]

Just a heads up, this is my first pull request. If I'm doing something wrong, please let me know.

I added some information that is specific to Rounded i3-gaps to the README.

• Changed title to Rounded i3-gaps from i3-gaps
• Added stuff explaining what Rounded i3-gaps is

Installation instructions:

• Added that it can be installed from AUR
• Changed link for install wiki to go directly to instructions for compiling
• Add note to set the correct repository for cloning

Help section:

• Add stuff specific to Rounded i3-gaps

Features section:

• Add instructions on how to configure rounded corners

[resloved]

Thanks for the PR! Originally I wasn't gonna change the README too much assuming we were aiming for a merge, but since that's not the case anymore this is probably a positive change. There's just a couple points of clarification to add, but besides those changes it looks good to me.

[bpetterborg]

Made requested changes

[resloved]

LGTM