docs: document steps to update CI pipeline

README.md

@@ -25,3 +25,19 @@ Original: Web Edition https://git.unlock-music.dev/um/web
 - Drag the encrypted file to `um.exe` (Tested on Windows)
 - Run: `./um [-o <output dir>] [-i] <input dir/file>`
 - Use `./um -h` to show help menu
+
+## Update CI pipeline
+
+Ensure `jsonnet` and `yq` is installed.
+
+```sh
+# Debian / Ubuntu etc:
+sudo apt install jsonnet yq
+```
+
+1. Edit `.drone.jsonnet`
+2. Update drone CI pipeline:
+
+   ```sh
+   jsonnet .drone.jsonnet | yq -y > .drone.yml
+   ```