Add dockerfile-mode to the prelude-auto-install-alist

core/prelude-packages.el

@@ -154,7 +154,8 @@ PACKAGE is installed only if not already present.  The file is opened in MODE."
     ("\\.scss\\'" scss-mode scss-mode)
     ("\\.slim\\'" slim-mode slim-mode)
     ("\\.textile\\'" textile-mode textile-mode)
-    ("\\.yml\\'" yaml-mode yaml-mode)))
+    ("\\.yml\\'" yaml-mode yaml-mode)
+    ("Dockerfile\\'" dockerfile-mode dockerfile-mode)))
 
 ;; markdown-mode doesn't have autoloads for the auto-mode-alist
 ;; so we add them manually if it's already installed