Added my Fedora COPR (experimental repo)

Today I tried to make SPEC file for slop.

I created a .spec file for slop and set up my COPR for building.  Also I
wrote [a script][1] that can produce the spec file and trigger new build from
sources at GitHub (my fork, for now):

  [1]: https://github.com/AloisMahdal/slop-copr-build

For now my plan is to keep an eye on new releases and re-run the script
manually (the script needs python-copr, which is only available at
Fedora AFAIK).

Should you consider providing "official" spec file, feel free to re-use
mine.

README.md

 * [Gentoo: x11-misc/slop](https://packages.gentoo.org/packages/x11-misc/slop)
 * [GNU Guix: slop](https://www.gnu.org/software/guix/packages/#slop)
 * [Debian: slop](https://packages.debian.org/sid/slop)
+* [Fedora COPR: amahdal/slop](https://copr.fedorainfracloud.org/coprs/amahdal/slop/) (experimental!)
 * Please make a package for slop on your favorite system, and make a pull request to add it to this list.
 
 ### Install using CMake (Requires CMake)