repo: add substation web interface

components/substation/docs/web_page.png

components/substation/html/css/w3.css

components/substation/html/favicon.ico

components/substation/html/images/control.png

components/substation/html/images/entity.png

components/substation/html/images/legos.png

components/substation/html/images/tower.png

components/substation/html/index.html

components/substation/include/substation.h

components/substation/src/substation.c

components/substation/substation.md

components/supermarket/supermarket.md