added passwordStrength estimator

src/test/password_test.ts

@@ -0,0 +1,12 @@
+import { check } from "./../util/passwordStrength";
+
+console.log(check("123456789012345"));
+// -> 0.25
+console.log(check("ABCDEFGHIJKLMOPQ"));
+// -> 0.25
+console.log(check("ABC123___...123"));
+// ->
+console.log(check(""));
+// ->
+// console.log(check(""));
+// // ->