Improve JSON detection: strip both ends, check matching brackets, use full content

src/rp/detect.py

@@ -90,10 +90,13 @@ def detect_type(
             return EXTENSION_MAP[suffix]
 
     if content is not None:
-        stripped = content.lstrip()
-        if stripped and stripped[0] in ("{", "["):
+        stripped = content.strip()
+        if stripped and (
+            (stripped[0] == "{" and stripped[-1] == "}")
+            or (stripped[0] == "[" and stripped[-1] == "]")
+        ):
             try:
-                json.loads(stripped[:1000])
+                json.loads(stripped)
                 return "json"
             except (json.JSONDecodeError, ValueError):
                 pass