To install it simply copy the "French Direct Numbers.keylayout" file in /System/Library/Keyboard Layouts/ directory.
REPO=https://raw.githubusercontent.com/akram/french-direct-numbers-keylayout/master/
wget $REPO/FrenchDirectNumbers.keylayout
wget $REPO/FrenchDirectNumbers.icns
sudo cp FrenchDirectNumbers.* /Library/Keyboard\ Layouts/
Then restart your finder (Force quit, then Relaunch on Finder process).
Then go to Keyboard menu in System preference pane and add "French #" as the keyboard layouts list. It should be located in the region name "Others".
Et voilà !!!!!