Add Async Functions to function templates

src/function-forms/default/async-arrow-function.template

src/function-forms/default/async-func-decl.template

src/function-forms/default/async-func-expr-named.template

src/function-forms/default/async-func-expr-nameless.template

src/function-forms/default/async-meth.template

...ion-forms/default/cls-decl-async-gen-meth-static.template

src/function-forms/default/cls-decl-async-gen-meth.template

...unction-forms/default/cls-decl-async-meth-static.template

src/function-forms/default/cls-decl-async-meth.template

...unction-forms/default/cls-expr-async-meth-static.template

src/function-forms/default/cls-expr-async-meth.template

src/function-forms/error/async-arrow-function.template

src/function-forms/error/async-func-decl.template

src/function-forms/error/async-func-expr-named.template

src/function-forms/error/async-func-expr-nameless.template

src/function-forms/error/async-meth.template

src/function-forms/error/cls-decl-async-meth-static.template

src/function-forms/error/cls-decl-async-meth.template

src/function-forms/error/cls-expr-async-meth-static.template

src/function-forms/error/cls-expr-async-meth.template