fix(lib/ace/autocomplete.js): customize auto-completion for Lean
fix(lib/ace/autocomplete.js): customize auto-completion for Lean

leanprover/ace,leanprover/ace,leanprover/ace,leanprover/ace,leanprover/ace,leanprover/ace,leanprover/ace,leanprover/ace,leanprover/ace,leanprover/ace,leanprover/ace,leanprover/ace,leanprover/ace,leanprover/ace,leanprover/ace,leanprover/ace,leanprover/ace,leanprover/ace