Add more information in the settings panel

[rdicosmo]

From an idea of Matthieu Haefele: replicate some information from the documentation into the plugin settings page to draw attention to the need to declare extra forges and/or add tokens.

For example:

• The little colored floppy icon does not appear on your porject page ? Likely the URL of your forge is not of the form gitlab.* or gitea.*, please add it here
• The little floppy icon got orange. API operations quota likely reached on github or SWH, please provide a token, ... or wait