format JSON snippets with jq.

doc/PLUGINS.md

@@ -225,7 +225,8 @@ A notification for topic `channel_opened` is sent if a peer successfully funded
 with us. It contains the peer id, the funding amount (in millisatoshis), the funding
 transaction id, and a boolean indicating if the funding transaction has been included
 into a block.
-```
+
+```json
 {
   "channel_opened": {
     "id": "03864ef025fde8fb587d989186ce6a4a186895ee44a926bfc370e2c366597a3f8f",
@@ -516,7 +517,9 @@ It is currently extremely restricted:
 
 ```json
 {
-  "writes": [ "PRAGMA foreign_keys = ON" ]
+  "writes": [
+    "PRAGMA foreign_keys = ON"
+  ]
 }
 ```