[Feature] Add calendar view for Todos in the home page

[amoraitis]

Is your feature request related to a problem? Please describe.
It would be nice, if we had a calendar view option in the home page, showing the todos of the current month.

Describe the solution you'd like

• Frontend
  Use bootstrap's tabs like buttons (I think that this requires bootstrap 4, in this case the present is blocked by Upgrade to BootstrapV4 #13 ) to navigate between views. Also, for the calendar view, use tables, at first, and see how that works. In each cell, we want only the titles of the Todos with each links at Todos/Details?id={id}

• Backend
  Another endpoint should be created at Todos/{month}-{year} to access the required resources.

Describe alternatives you've considered
Use an existing calendar view, but in this case, let's build something from scratch...

Additional context
We need a viewmodel for the new page, to request only the data we need.

[pirland]

I can work on this once my changes in #51 pass.