docs: Add symbols index for 1.8
docs: Add symbols index for 1.8

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