feat: optgroup dividers in unit dropdown, matching group order and visibility

data/units.json

@@ -98,13 +98,14 @@
       "hidden": false
     },
     {
-      "id": "asdf",
-      "label": "asdf",
-      "labelPlural": "asdf",
-      "symbol": "asdf",
-      "group": "another-group",
+      "id": "mm",
+      "label": "millimeter",
+      "labelPlural": "millimeters",
+      "symbol": "mm",
+      "group": "lengths-and-distance",
       "toBase": 1,
-      "hidden": true
+      "hidden": false,
+      "description": "It's so tiny and kawaii (♡‿♡)."
     },
     {
       "id": "pound",
@@ -138,6 +139,14 @@
       "symbol": "t",
       "group": "dickloads",
       "toBase": 76
+    },
+    {
+      "id": "cm",
+      "label": "centimeter",
+      "labelPlural": "centimeters",
+      "symbol": "cm",
+      "group": "lengths-and-distance",
+      "toBase": 10
     }
   ],
   "groups": [
@@ -151,12 +160,12 @@
       "alwaysShowLabel": true
     },
     {
-      "id": "another-group",
-      "label": "Another Group",
-      "baseUnitId": "",
+      "id": "lengths-and-distance",
+      "label": "Lengths and Distance",
+      "baseUnitId": "mm",
       "toUniversal": 1,
       "alwaysShowLabel": false,
-      "hidden": true
+      "hidden": false
     }
   ]
 }