doc: Add API index for highlight foreground color
doc: Add API index for highlight foreground color

flaxandteal/gasket-vte,rvu95/vte,flaxandteal/gasket-vte,jessevdk/vte,flaxandteal/gasket-vte,flaxandteal/gasket-vte,rvu95/vte,pjm0616/vte,rvu95/vte,saitoha/vte-sixel,rvu95/vte,jessevdk/vte,jessevdk/vte,pjm0616/vte,saitoha/vte-sixel,pjm0616/vte,thestinger/vte-ng,jessevdk/vte,saitoha/vte-sixel,thestinger/vte-ng,thestinger/vte-ng