minor: form feedbacks

Contains:

• #575 (closed) Order on skills select, partially blocked by framework/sib-core#668 (closed) - will not need any action on our side after the core fix
• #710 (closed) Toast feedback on form success
• #710 (closed) Required fields coherence (Star only when required)
• #710 (closed) Validation on username, email, website fields
• #529 (closed) Do not display the icon on missing profile field
• Fix for the link to Make Hubl Better on dashboard
• Adapted tests for these new behaviors

I had no way to provide feedback on error after submitting a form, but with required and validations I also had no way to reach this case now.