Update of the README.md file in order to display the 2 update sites download links.
Update of the README.md file in order to display the 2 update sites
download links.

ymortier/Capella-Extensions,ObeoNetwork/Capella-Extensions,ObeoNetwork/Capella-Extensions,ymortier/Capella-Extensions,ymortier/Capella-Extensions,ObeoNetwork/Capella-Extensions