chore(library/congr_lemma_manager): document main methods
chore(library/congr_lemma_manager): document main methods

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