Add some gtk-doc comments
Add some gtk-doc comments

While trying to understand this code.

gloob/vte-copy,rvu95/vte,flaxandteal/gasket-vte,jessevdk/vte,pjm0616/vte,asivokon/vte-fx,saitoha/vte-sixel,asivokon/vte-fx,aligo/vte,saitoha/vte-sixel,asivokon/vte-fx,rvu95/vte,gloob/vte-copy,gloob/vte-copy,flaxandteal/gasket-vte,aligo/vte,pjm0616/vte,flaxandteal/gasket-vte,jessevdk/vte,saitoha/vte-sixel,thestinger/vte-ng,rvu95/vte,jessevdk/vte,jessevdk/vte,rvu95/vte,pjm0616/vte,aligo/vte,thestinger/vte-ng,flaxandteal/gasket-vte,thestinger/vte-ng,asivokon/vte-fx