feat: Implement a mathematical implication

lib/math.dart

@@ -0,0 +1,4 @@
+/// A mathematical implication between [a] and [b] (a -> b);
+bool implies(bool a, bool b) {
+  return !a || b;
+}

lib/moxlib.dart

@@ -2,3 +2,4 @@ library moxlib;
 
 export "awaitabledatasender.dart";
 export "automaton.dart";
+export "math.dart";