Split into multiple files (#57)

* Create all files

* Split everything into its own file

* Use those individual files in index.ts

* prettier

* Add imports that I forgot 🤣

* Use explicit .js suffix for compat with #55

src/getType.ts

@@ -0,0 +1,9 @@
+/**
+ * Returns the object type of the given payload
+ *
+ * @param {*} payload
+ * @returns {string}
+ */
+export function getType(payload: any): string {
+  return Object.prototype.toString.call(payload).slice(8, -1)
+}