chore: add typescript usage example

Author: sciborrudnicki

packages/type/src/is/usage/is-not-undefined.ts

@@ -0,0 +1,25 @@
+import { is } from '../lib/is.object';
+
+// Example usage with the problem
+interface Config {
+  a?: string;
+  b?: string;
+}
+const config: Config = {
+  a: 'x',
+  b: 'y'
+};
+
+function configFunction(value: string): string {
+  return '';
+}
+
+// Cause typescript returns `boolean` this will generate a type error
+if (is.not.undefined(config.a)) {
+  configFunction(config.a);
+}
+
+// Cause typescript return `value is undefined` will not generate an error
+if (!is.undefined(config.a)) {
+  configFunction(config.a);
+}