Added example to transform FormData to zip

documentation/howto/formdata_to_zip.md

@@ -0,0 +1,37 @@
+---
+title: "How to create a zip from a FormData object"
+layout: default
+section: example
+---
+
+When submitting a `multipart/form-data`, a FormData can be generated automatically:
+
+```js
+$(form).on('submit', e => {
+  e.preventDefault();
+  const form = new FormData(e.target);
+
+  // ...
+});
+```
+
+To convert from the FormData to zip all of the files, you can parse it easily and add all of the files to the zip:
+
+```js
+$('form#myform').on('submit', e => {
+  e.preventDefault();
+  const form = new FormData(e.target);
+
+  const zip = new JSZip()
+  for (let [key, value] of form.entries()) {
+    if (value instanceof File) {
+      zip.file(key, value);
+      form.delete(key);   // No longer needed it here
+    }
+  }
+
+  // ...
+});
+```
+
+Now you have all of the files uploaded in the form within a single zip, and can proceed with it as you desire.