fix(lib): leave point at bob in with-file-contents!

with-file-contents!'s docstring promises that point will end up at the
beginning of the buffer, but this promise wasn't kept until now.

lisp/lib/files.el

@@ -342,6 +342,7 @@ optimizations for `binary' IO."
   (declare (indent 1))
   `(doom--with-prepared-file-buffer ,file (or coding-system-for-read 'utf-8) nil
      (doom-file-read buffer-file-name :by 'insert :coding coding-system-for-read)
+     (goto-char (point-min))
      ,@body))
 
 ;;;###autoload