NPM update procedure on homebridge-raspbian-image

<!--
You must use the issue template below when submitting a support request
-->

<!--
If you are having an issue with a certain plugin, please raise the issue on that plugin's project page instead.
-->

<!--
The Homebridge Raspberry Pi image is just Raspbian Linux with Homebridge installed as a service.
If you are facing an issue that is not Homebridge related you should look elsewhere for support.
-->

**Describe Your Problem:**
Hi.  All my config works ok and is up to date (Homebridge, Pi hole and Node-Red).  I am trying to update NPM to the latest version, but I don't see any option through Config UI X and neither through "hb-config" under Terminal. I don't see any in the Wiki, and I don't want to break it all.

Should I run "sudo npm install -g npm" under Terminal as I see in the Homebridge on Raspbian Wiki? or that will break all.

Sorry if this is not the correct place to ask this question, and thanks :)

<!-- A clear and concise description of what problem you are trying to solve. -->

**Screenshots:**
![Captura de pantalla 2020-05-09 a las 12 10 04](https://user-images.githubusercontent.com/64600283/81470948-1643af80-91ee-11ea-8940-0f357350da43.png)
![Captura de pantalla 2020-05-09 a las 13 29 17](https://user-images.githubusercontent.com/64600283/81472573-52c8d880-91f9-11ea-8c0e-a9b83e3a5684.png)
<!-- If applicable, add screenshots to help explain your problem. -->

**Environment:**

* **Homebridge Raspberry Pi Image Version**: v1.0.2
* **Node.js Version**: <!-- node -v --> v12.16.3
* **NPM Version**: <!-- npm -v --> v6.14.4
* **Homebridge Version**: <!-- homebridge -V --> v1.0.4
* **Homebridge Config UI X Plugin Version**: <!-- hb-service -v --> v4.18.0

<!-- Click the "Preview" tab before you submit to ensure the formatting is correct. -->
