useProps: Add doc comment

src/utils/use-props.js

@@ -1,14 +1,20 @@
 import { ref } from "vue";
 
-export default function useProps(src, props) {
+// useProps takes an object and turns select props into refs.
+// The mapping is an object whose keys are turned into names on returned data object.
+// The values of the mapping are the names of the props on source object
+// and then optional transformations to do on deserialize and serialize.
+export default function useProps(src, mapping) {
   const data = {};
-  for (let [prop, [name, wrap = (v) => v]] of Object.entries(props)) {
-    data[prop] = ref(wrap(src[name]));
+  for (let [prop, [name, deserialize = (v) => v]] of Object.entries(mapping)) {
+    data[prop] = ref(deserialize(src[name]));
   }
   function saveData() {
     let dst = {};
-    for (let [prop, [name, , unwrap = (v) => v]] of Object.entries(props)) {
-      dst[name] = unwrap(data[prop].value);
+    for (let [prop, [name, , serialize = (v) => v]] of Object.entries(
+      mapping
+    )) {
+      dst[name] = serialize(data[prop].value);
     }
     return dst;
   }