Add info about npm requiring path (openhab#17022)

The command to install an npm package that was suggested in the documentation would not work, as it was missing the required path. I've added information to explain this is required.

Signed-off-by: SkyLined <[email protected]>

bundles/org.openhab.automation.jsscripting/README.md

@@ -1429,7 +1429,7 @@ Follow these steps to create your own library (it's called a CommonJS module):
    ```
 
 4. Tar it up by running `npm pack` from your library's folder.
-5. Install it by running `npm install <name>-<version>.tgz` from the `automation/js` folder.
+5. Install it by running `npm install <path-to-library-folder>/<name>-<version>.tgz` from the `automation/js` folder.
 6. After you've installed it with `npm`, you can continue development of the library inside `node_modules`.
 
 It is also possible to upload your library to [npm](https://npmjs.com) to share it with other users.