Visually indicate request processing

[Mateusz-Dobrzynski]

We need some way to indicate that a request is being processed. Case in point: when hitting "Enter" to log in, nothing happens until the auth request gets processed. This feedback-lacking design must be changed.

TO-DO:

• Create a reusable visual loading indicator:
  • Make submit buttons play a pulse animation when requests are being processed,
  • Change cursor to wait.

How to test:

• Test login and language change flows. When clicking confirmation buttons, expect a loading animation to appear and the cursor to be changed to wait. Once the response is presented, the interface should go back to normal.

[Mateusz-Dobrzynski]

@jakubmanczak, I request your input regarding what loading animation to choose. MoonLoader is probably the most standard one, BarLoader is also nice. We could also use PuffLoader, if we're feeling fancy.

[jakubmanczak]

I'm not sure what kind of feedback you're seeking here; how would these be applied? As an icon next to the button, or are those supposed to be sunken into the button's bg? If the latter, I suppose it doesn't matter much.