docs(readme): Briefly explain how to build and install plugins

Signed-off-by: Sebastian Schuberth <[email protected]>

Author: sschuberth

README.md

@@ -5,6 +5,13 @@ This is a template Gradle project to create a package manager plugin for the [an
 # Usage
 
 Create a new repository [from this template], clone it, and replace all occurrences of "MyPackageManager" (search for case-insensitive substrings) with the name of the package manager you are implementing.
+Then implement the actual package manager, and when done, run
+
+```shell
+./gradlew installDist
+```
+
+Finally, copy `./build/install/MyPackageManager/*.jar` to the `plugin` direct of the ORT installation (`/opt/ort/plugin` in ORT's official Docker images).
 
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