feat: add SIMON i7 2g dimmer light switch

[flaskr]

Add support for SIMON's 2g dimmer switches. This allows control and state(On/Off/Brightness) reporting for both 'Left' and 'Right' gang switches.

[Koenkk]

Could you provide a link to the product page of this device?

[flaskr]

Here's one of the catalogues for this model
https://simonkorea.com/theme/basic/pdf/spec_0201-18.pdf

[Koenkk]

Thanks!

Could you also submit a picture for the docs? This can be done by:

1. Create a fork by clicking here
2. Go to the public/images/devices directory, Add file -> Upload files
3. Upload the files and press Commit changes
4. Press Contribute -> Open pull request -> update title/description -> Create pull request

Make sure that:

• The filename is SM0502.png
• The size is 512x512
• The background is transparent (use e.g. Adobe remove background)