doc: schemas for everything else.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Changelog-Fixed: doc: Epic documentation rewrite: each now lists complete and accurate JSON output, tested against testsuite.

doc/schemas/dev-sendcustommsg.schema.json

@@ -0,0 +1,11 @@
+{
+    "$schema": "http://json-schema.org/draft-07/schema#",
+    "type": "object",
+    "required": [ "status" ],
+    "properties": {
+        "status": {
+            "type": "string",
+            "description": "Information about where message was queued"
+        }
+    }
+}