Switch fixing header to top when resizing window to mobile width

[fabian-beck]

Treat isMobile as a reactive property

[thetejasmagade]

Header, should be fixed on top on mobile devices? Could, you elaborate more on this?

[fabian-beck]

When loading the page at a mobile resolution, the header (menu bar) is already fixed at the top. When resizing the window from a desktop resolution to mobile, this property does not automatically update, however. The header will scroll out.

Only a very minor issue, as I suspect only few users will switch the mode in this style.

[fabian-beck]

Solved through migrating to Vuetify #413