Support changing position of the dock

[manu20247]

It would be very positive to add the following settings to the Dock: Move it to the right or left side of the screen. And that these settings are located in "system settings" "desktop" "Dock". It would be interesting to be able to change its theme as well, but that's not so important. It would be fun, but for now the option to change its placement on the screen is the most important thing.

[ryonakano]

Duplicate of #230