show known types in form

static/form.html

@@ -30,6 +30,7 @@
       
       <label for="type">Type</label>
       <input id="type" type="text">
+      <p id="knowntypes"></p>
       
       <label for="name">Name / Label</label>
       <input id="name" type="text">

static/form.js

@@ -12,6 +12,7 @@ document.onreadystatechange = function() {
 
 function fillForm() {
   const item = items[id];
+  knownTypes();
 
   const is_in = document.getElementById('is_in');
 
@@ -52,6 +53,17 @@ function fillForm() {
   }
 }
 
+function knownTypes() {
+  let map = {};
+  for (const i of Object.values(items)) {
+    if (i.type) {
+      map[i.type] = true;
+    }
+  }
+  let types = Object.keys(map).sort().join(', ')
+  document.getElementById('knowntypes').textContent = `Known types: ${types}.`;
+}
+
 function save() {
   item = {
     id: document.getElementById('id').value || null,