Implement application form

[jodator]

sub-task for #293 

Requirements:

• Fetch opening questions from the API
• Implement form builder for given application schema.
• Implement the "TEXT" field for text input.
• Implement the "TEXTAREA" using a Markdown editor. See Add markdown processor #448
• Consult the need for "Visual" / "Text" / "Preview" tabs

[jodator]

So I've added CKEditor to the form, but the lack of typing is sad (ckeditor/ckeditor5#504).

I can however add typings for the React component to have at least this typed.