feat(emacs/lean-syntax): add syntax-highlight for declaration modifiers
feat(emacs/lean-syntax): add syntax-highlight for declaration modifiers

Signed-off-by: Leonardo de Moura <7610bae85f2b530654cc716772f1fe653373e892@microsoft.com>

fpvandoorn/lean2,Kha/lean,eigengrau/lean,soonhokong/lean,dselsam/lean,fpvandoorn/lean2,fgdorais/lean,javra/lean,c-cube/lean,soonhokong/lean-osx,fpvandoorn/lean,fpvandoorn/lean2,levnach/lean,c-cube/lean,leodemoura/lean,eigengrau/lean,soonhokong/lean-windows,eigengrau/lean,dselsam/lean,dselsam/lean,johoelzl/lean,htzh/lean,leanprover-community/lean,c-cube/lean,avigad/lean,levnach/lean,fgdorais/lean,leodemoura/lean,soonhokong/lean-osx,johoelzl/lean,javra/lean,Kha/lean,rlewis1988/lean,UlrikBuchholtz/lean,htzh/lean,soonhokong/lean,soonhokong/lean-osx,eigengrau/lean,avigad/lean,c-cube/lean,Kha/lean,leanprover/lean,johoelzl/lean,dselsam/lean,rlewis1988/lean,levnach/lean,rlewis1988/lean,digama0/lean,leodemoura/lean,Kha/lean,levnach/lean,fgdorais/lean,fpvandoorn/lean,javra/lean,leanprover-community/lean,sp3ctum/lean,Kha/lean,UlrikBuchholtz/lean,soonhokong/lean-osx,soonhokong/lean,fpvandoorn/lean,avigad/lean,digama0/lean,Kha/lean,johoelzl/lean,leanprover-community/lean,UlrikBuchholtz/lean,johoelzl/lean,leanprover/lean,soonhokong/lean-windows,avigad/lean,htzh/lean,soonhokong/lean-windows,sp3ctum/lean,fpvandoorn/lean2,leanprover/lean,leanprover-community/lean,sp3ctum/lean,leodemoura/lean,rlewis1988/lean,fpvandoorn/lean,eigengrau/lean,leanprover-community/lean,c-cube/lean,soonhokong/lean-osx,leanprover/lean,leodemoura/lean,soonhokong/lean,leanprover/lean,leodemoura/lean,soonhokong/lean-windows,sp3ctum/lean,avigad/lean,levnach/lean,UlrikBuchholtz/lean,htzh/lean,fgdorais/lean,digama0/lean,rlewis1988/lean,htzh/lean,digama0/lean,digama0/lean,fpvandoorn/lean,javra/lean,UlrikBuchholtz/lean,fpvandoorn/lean,soonhokong/lean-windows,dselsam/lean,digama0/lean,sp3ctum/lean,leanprover/lean,johoelzl/lean,fgdorais/lean,avigad/lean,soonhokong/lean,fgdorais/lean,leanprover-community/lean,fpvandoorn/lean2,dselsam/lean,javra/lean,rlewis1988/lean