Create edit participant component

[OtisRed]

General description
We need a possbility to edit details of the participant that has been already added to the database.

Technical description
We could probably override the logic of create participant form with condition that if a user already exists the component uses different endpoint to PUT data, rather than POST it.

Nevertheless the form should contain fields:

• first name
• last name
• email
• phone
• github account
• slack nick