Add Roborock S7 to tested vacuums

[jdejaegh]

First, thanks for this project!

I managed to have my Roborock S7 working, using v0.0.2-rc1. The official Roborock app also works as described in the documentation. I had to do the following things to have it work:

• Use Actalis CA instead of Let's Encrypt
• Accept all credentials from MQTT clients Learn unknown device MQTT credentials on first connect #22 (comment) (maybe this is fixed in the most recent version, I did not test)

[Lash-L]

Thank you!