feat(cpp): add selection version to most of postfix snippets

feat(cpp): add a new snippets, and can disable cpplint comments now

fix(rust): primitive_type as type

fix(cond): check matched trigger, fix #3

feat(cpp,config): new config to add more quick_type shortcuts

feat(nix): add .split postfix to bindings

doc(nix): nix snippets doc

feat(rust): add `tfn` snippet