Allow ML-style block comments [recommendation]

[nikita-fuchs]

As plenty syntax highlighters for functional languages use (* *) for block comments by default

[radrow]

Personally I don't like this notation, because if we wanted to add prefix notation of operators (i.e. `a + b == (+)(a, b)`) the `(*)` function would cause some problems. Also, `//` and `/*` are more popular than `(* *)` which are common only in ML like languages.

Also, this should be moved to aesophia repo