docs(readme): Add installation instructions

Author: Madman10K

README.md

@@ -1,2 +1,11 @@
-# metacraft-overlay
-Our gentoo overlay
+# The Metacraft Labs Gentoo overlay
+This is our Gentoo overlay where we store our Gentoo ebuilds for applications such as [CodeTracer](https://codetracer.com).
+
+## Subscribing
+You can subscribe to the overlay via `eselect`:
+```
+root # eselect repository add metacraft-overlay git https://github.com/metacraft-labs/metacraft-overlay.git
+```
+
+## Contributing
+Issues, PRs and discussions on the packages can be found on the [GitHub repository](https://github.com/metacraft-labs/metacraft-overlay).