Fix #13, make youtube API optional

src/lib/truthyString.ts

@@ -0,0 +1,7 @@
+export function isTruthy(value: string | number | boolean | null | undefined): boolean {
+  if (typeof value === 'string') {
+    return value.toLowerCase() === 'true' || !!+value; // here we parse to number first
+  }
+
+  return !!value;
+}