Add a hash util function.

Not particularly secure or anything, just looking for something consistent.

Used the same one as card-web.

Part of #55. Part of #25.

src/util.ts

@@ -43,4 +43,15 @@ export const setObjectProperty = (obj : NormalObject, path : string, value : unk
 	const subObject = isNaN(parseInt(parts[1])) ? {} : [];
 	obj[parts[0]] = subObject;
 	setObjectProperty(obj[parts[0]] as NormalObject, parts.slice(1).join('.'), value);
+};
+
+export const hash = (str : string) => {
+	//Adapted from https://stackoverflow.com/questions/7616461/generate-a-hash-from-string-in-javascript
+	let hash = 0, i, chr;
+	for (i = 0; i < str.length; i++) {
+		chr   = str.charCodeAt(i);
+		hash  = ((hash << 5) - hash) + chr;
+		hash |= 0; // Convert to 32bit integer
+	}
+	return hash;
 };