Support for "$" syntax to indicate where the serialization logic should collect values into arrays.

Use a dollar sign to indicate where tp-form should collect values as an
array. For example `myfield.$list.value` collects { myfield: { list: [ {
value: '...' } ] } }

package.json

@@ -1,6 +1,6 @@
 {
   "name": "@tp/tp-form",
-  "version": "1.1.1",
+  "version": "1.2.0",
   "description": "",
   "main": "tp-form.js",
   "scripts": {