add colorpicker to Web-UI

[Staars]

Some users asked for the possibility to control color lights outside of a home automation system. This PR adds a small color picker/slider to the Web-GUI.

The main goal was to keep this as tiny as possible with a slight amount of responsiveness. It should show up automatically for devices configured for color lights.

This adds 756 bytes of program space.

[ascillato]

Tested and works! 👍

[jziolkowski]

It was tested by 2.5 and 7.5yo at our home and the verdict is "Absolutely great!"

[Staars]

It looks like that:

[ascillato]

On a NodeMCU with a relay and a WS2812B Led Strip, it looks like:

[ihavenonick]

This is a Magic Home RGBW and i miss a Slider for real white color. its onli a Slider for RBG an not for white. I use IOBroker and there are data points for white an a dimmer also.
Its not posilble to control color white with the webinterface, only wjth IOBroker over MQTT.

I uses this template for RGBW stripe:
{"NAME":"MH-RGBW","GPIO":[255,255,255,255,255,38,255,255,37,39,0,40,255],"FLAG":15,"BASE":18}

[Staars]

We are still in the process of finalizing the things.
Keep in mind, that Tasmota uses a HSB-color-model and NOT HSL internally. So the creation of white needs desaturation.
Please be patient and wait for the new WIKI entry, which will likely be delayed a bit, because the whole WIKI gets a new technical base. This will take a bit longer than usual.

[ihavenonick]

OK, it means something is coming for white?