docs: reinstate install docs on README [ci skip]

README.md

@@ -9,6 +9,20 @@ The Co-op Cloud utility belt 🎩🐇
 
 `abra` is a command-line tool for managing your own [Co-op Cloud](https://coopcloud.tech). It can provision new servers, create apps, deploy them, run backup and restore operations and a whole lot of other things. Please see [docs.coopcloud.tech](https://docs.coopcloud.tech) for more extensive documentation.
 
+## Quick install
+
+```bash
+curl https://install.abra.autonomic.zone | bash
+```
+
+Or using the latest release candidate (extra experimental!):
+
+```bash
+curl https://install.abra.autonomic.zone | bash -s -- --rc
+```
+
+Source for this script is in [scripts/installer/installer](./scripts/installer/installer).
+
 ## Hacking
 
 ### Getting started