user/rmpc: new package

[aniruddhgutta]

Description

Rmpc is a beautiful, modern and configurable terminal based Music Player Daemon client. It is heavily inspired by ncmpcpp and ranger/lf file managers.

Checklist

Before this pull request is reviewed, certain conditions must be met.

The following must be true for all changes:

• I have read CONTRIBUTING.md
• I acknowledge that overtly not following the above or the below will result in my pull request getting closed

The following must be true for template/package changes:

• I have read Packaging.md
• I have built and tested my changes on my machine

The following must be true for new package submissions:

• I will take responsibility for my template and keep it up to date