Add authentication to opsdroid web

[FabioRosado]

The goal for opsdroid web v2 is to work together with opsdroid's command center (opsdroid/opsdroid#1872). On the open PR that implements the command center, we require users to provide a token in which we can toggle modules on/off.

As part of #20 we should allow users to provide a token in which we can use to authenticate the user and interactions between opsdroid web and opsdroid itself.

[FabioRosado]

Perhaps we should show a sort of 'log in' kind of form which asks users to input their token if they want to interact with opsdroid.

That way we should be good to show all information to authenticated users. Perhaps we may need to do some extra bits in opsdroid to make sure we are using the token properly?

[FabioRosado]

This work is currently blocked until we implement opsdroid/opsdroid#1932