Export source code as GitHub gist

• There should be a new button under File actions to export (name: Gist it)
• A new GitHub gist with the current file content should be created after clicking on the button
• The editor should open the diagram from the gist url after the export operation is done

For this to work, the user should be authenticated on GitHub via their personal access token with the gist permission set

• After clicking on the button, a popup should be presented to the user if they haven't set their token yet
• Tokens should be saved as browser cookies
• The popup should inform the user the reason why they need the token
• There should be links to guide the user on how to create tokens and to the token page