js: fix rand build, properly use key values on map, add rand.string (#12020)

vlib/rand/wyrand/wyrand.js.v

@@ -0,0 +1,3 @@
+module wyrand
+
+pub fn (mut r WyRandRNG) free() {}

vlib/rand/wyrand/wyrand.v

@@ -250,9 +250,3 @@ pub fn (mut rng WyRandRNG) f64_in_range(min f64, max f64) f64 {
 	}
 	return min + rng.f64n(max - min)
 }
-
-// free should be called when the generator is no longer needed
-[unsafe]
-pub fn (mut rng WyRandRNG) free() {
-	unsafe { free(rng) }
-}

vlib/rand/wyrand/z_wyrand.c.v

@@ -0,0 +1,7 @@
+module wyrand
+
+// free should be called when the generator is no longer needed
+[unsafe]
+pub fn (mut rng WyRandRNG) free() {
+	unsafe { free(rng) }
+}