Add support for OctoPrint-TPLinkSmartplug as a plugin on OctoDash

[xunleii]

- Firstly, thanks a lot for this project, it is awesome. -

Is your feature request related to a problem? Please describe.
I personally use OctoPrint-TPLinkSmartplug to power on/off my printer, instead of PSUControl.

Describe the solution you'd like
I'd like to power off my printer when OctoDash is exiting from sleep mode and, like for PSUControl, add custom actions (like [!TPLINKON], [!TPLINKOFF] and [!TPLINKTOGGLE]).

Link other projects

• OctoPrint-TPLinkSmartplug: https://plugins.octoprint.org/plugins/tplinksmartplug/

Additional context
I think it could be straightforward to support it on OctoDash, because the plugin has an API (and a wiki), and works like PSUControl (on/off action available (+ status for toggle action)). The main difference is that we have to specify an IP address when we want to change the state of the SmartPlug.