support form: add error and success notifications for frontend

[alejandromumo]

The new support form does not display any success / error messages to the user. The only error messages that are displayed come from Formik form validation (using Yup)

The new support form is currently implemented in #61

In this issue:

• Evaluate how error messages (not validation) are displayed in the support form
• Display a notification when an error occurs in the backend (e.g. e-mail not sent) or when the form was sent (in case of success).

See the current form

[alejandromumo]

Screenshots:

[alejandromumo]

Closing this in favor of #81