Read the CSS breakpoint in Angular

[Jogo27]

This ticket is part of the information panel work. This is a prototype ticket to prepare the implementation of ResponsiveBreakpointService. The aim of this ticket is to display the value of a breakpoint.

• Turn the SASS breakpoint variables (of the form $breakpoint-something) into CSS variables (of the form --breakpoint-something).
• Add a typescript variable of type string in PollComponent to store the value of a breakpoint.
• In the method ngOnInit of PollComponent, retrieve the value of one CSS breakpoint variable and store it in the new variable. Look at this for help.
• Display the variable in the html file of PollComponent, using text interpolation.