repo: add power_plant web interface

components/power_plant/docs/web_page.png

components/power_plant/html/css/w3.css

components/power_plant/html/favicon.ico

components/power_plant/html/images/entity.png

components/power_plant/html/images/legos.png

components/power_plant/html/images/load_high.png

components/power_plant/html/images/load_low.png

components/power_plant/html/images/meter.svg

components/power_plant/html/images/tower.png

components/power_plant/html/index.html

components/power_plant/include/power_plant.h

components/power_plant/power_plant.md

components/power_plant/src/power_plant.c