Add 'level' reporting to mirror position

[joshualyon]

Improve compatibility with automations and other apps by also reporting the 'level' attribute since the device declares the Switch Level capability.

[joshualyon]

For full compatibility, the Switch capability should also be implemented. For example, mirroring the "open" state to "on" and the "closed" state to "off".

This initial PR resolves a request by a SharpTools.io dashboard user where the level attribute is needed. I left the 'switch' mapping out of the initial PR in case you, the original driver author, had a preference on the mapping. (eg "open"="on", "closed"="off" or the reverse with "closed"="on", "open"="off")

[Kick4U2]

Hello! Not sure if you found my fork useful, but I have included the switch and dimmer capabilities for automating with other devices and systems. I use Lutron keypads and toggle my shades by creating a virtual shade within Ra2.