document arg, functor, conditionals

README.md

@@ -78,11 +78,15 @@ The following predicates are built-in to rusty-wam.
     * Comparison operators: `>`, `<`, `=<`, `>=`, `=:=`, `=\=`.
 * `(\+)/1`
 * `(=)/2`
+* `(->)/2`
+* `(;)/2`
+* `arg/3`
 * `atomic/1`
 * `call/N` (1 <= N <= 63)
 * `catch/3`
 * `duplicate_term/2`
 * `false/0`
+* `functor/3`
 * `integer/1`
 * `throw/1`
 * `true/0`