syntax/json: Add comment support to the syntax highlighting (zyedidia#3434)

* allow comments in json

* syntax/json: Add colon to `TODO` comments

---------

Co-authored-by: Sertonix <[email protected]>

Author: JoeKar

runtime/syntax/json.yaml

@@ -25,3 +25,15 @@ rules:
 
     - statement: "\\\"(\\\\\"|[^\"])*\\\"[[:space:]]*:\"  \"'(\\'|[^'])*'[[:space:]]*:"
     - constant: "\\\\u[0-9a-fA-F]{4}|\\\\[bfnrt'\"/\\\\]"
+
+    - comment:
+        start: "//"
+        end: "$"
+        rules:
+            - todo: "(TODO|XXX|FIXME):?"
+
+    - comment:
+        start: "/\\*"
+        end: "\\*/"
+        rules:
+            - todo: "(TODO|XXX|FIXME):?"