grammar: fix structure of coments in block bodies

src/grammar.json

@@ -23,20 +23,46 @@
       ]
     },
     "body": {
-      "type": "REPEAT1",
-      "content": {
-        "type": "CHOICE",
-        "members": [
-          {
-            "type": "SYMBOL",
-            "name": "attribute"
-          },
-          {
-            "type": "SYMBOL",
-            "name": "block"
-          }
-        ]
-      }
+      "type": "CHOICE",
+      "members": [
+        {
+          "type": "SYMBOL",
+          "name": "_shim"
+        },
+        {
+          "type": "SEQ",
+          "members": [
+            {
+              "type": "CHOICE",
+              "members": [
+                {
+                  "type": "SYMBOL",
+                  "name": "_shim"
+                },
+                {
+                  "type": "BLANK"
+                }
+              ]
+            },
+            {
+              "type": "REPEAT1",
+              "content": {
+                "type": "CHOICE",
+                "members": [
+                  {
+                    "type": "SYMBOL",
+                    "name": "attribute"
+                  },
+                  {
+                    "type": "SYMBOL",
+                    "name": "block"
+                  }
+                ]
+              }
+            }
+          ]
+        }
+      ]
     },
     "attribute": {
       "type": "SEQ",
@@ -1779,6 +1805,10 @@
     {
       "type": "SYMBOL",
       "name": "heredoc_identifier"
+    },
+    {
+      "type": "SYMBOL",
+      "name": "_shim"
     }
   ],
   "inline": [],

src/node-types.json

@@ -139,7 +139,7 @@
     "fields": {},
     "children": {
       "multiple": true,
-      "required": true,
+      "required": false,
       "types": [
         {
           "type": "attribute",