docs: Add the 1.12 symbols index to the API reference
docs: Add the 1.12 symbols index to the API reference

ebassi/clutter,djdeath/clutter,djdeath/clutter-android,kerrickstaley/clutter-vala,kerrickstaley/clutter-vala,heysion/clutter-clone,djdeath/clutter,djdeath/clutter,collects/clutter,jigpu/clutter,jigpu/clutter,heysion/clutter-clone,Distrotech/clutter,djdeath/clutter,Distrotech/clutter,Distrotech/clutter,heysion/clutter-clone,GNOME/clutter,djdeath/clutter-android,collects/clutter,Distrotech/clutter,kerrickstaley/clutter-vala,jigpu/clutter,heysion/clutter-clone,jigpu/clutter,ebassi/clutter,GNOME/clutter,ebassi/clutter,ebassi/clutter,GNOME/clutter,djdeath/clutter-android,GNOME/clutter,collects/clutter,djdeath/clutter,ebassi/clutter,Distrotech/clutter,djdeath/clutter-android,djdeath/clutter-android,Distrotech/clutter,jigpu/clutter,collects/clutter,djdeath/clutter,collects/clutter,GNOME/clutter,jigpu/clutter,heysion/clutter-clone,kerrickstaley/clutter-vala