Add json-mode entry to `magic-mode-alist'

Author: notetiene

json-mode.el

@@ -116,6 +116,9 @@ This function calls `json-mode--update-auto-mode' to change the
   "Major mode for editing JSON files"
   (set (make-local-variable 'font-lock-defaults) '(json-font-lock-keywords-1 t)))
 
+;; Well formatted JSON files almost always begin with “{” or “[”.
+(add-to-list 'magic-mode-alist '("^[{[]$" . json-mode))
+
 ;;;###autoload
 (defun json-mode-show-path ()
   (interactive)