mgr/dashboard: Add submit button component

mgr/dashboard: Add submit button component

This component is to be used inside a form.

It will render a submit button with the given label.
The button will disabled itself and show a loading icon when the user clicks it,
usually initiating a request to the server, and it will stay in that state
until the request is finished.

To indicate that the request failed, returning the button to the enable state,
you need to insert an error in the form with the 'cdSubmitButton' key.

It will also check if the form is valid, when clicking the button, and will
focus on the first invalid input.

Signed-off-by: Tiago Melo <tmelo@suse.com>