Make Sign in button on Login purple

[ChaelCodes]

Describe the Feature

Is your feature request related to a problem? Please describe.
The login/signup screen are half-styled. Let's improve these by bulma-izing them.

Additional context

Describe the Technical Implementation of the Solution

Solution
We have an ApplicationFormBuilder now that might accept a submit method. Otherwise, you might have to generate the devise views. Finding a way to override the button is preferred to generating all the views in our app. In bulma, we'd apply the class is-primary.

References
Any references to materials or help articles that may help in implementing this issue.

[ChaelCodes]

@ChaelCodes Finish writing this. Include devise template and Matthew's fancy formbuilder.

[sjaustirni]

This issue seems to be fixed now, the button is visibly purple and of style is-primary: https://hunters-keepers.herokuapp.com/users/sign_in