libraries: convert urlUtils to TypeScript (prebid#13497)

Author: patmmccann

libraries/urlUtils/urlUtils.js

@@ -0,0 +1,7 @@
+export function tryAppendQueryString(existingUrl: string, key: string, value: string): string {
+  if (value) {
+    return `${existingUrl}${key}=${encodeURIComponent(value)}&`;
+  }
+
+  return existingUrl;
+}