## What changes were proposed in this pull request?

add header

## How was this patch tested?

Manual run to check vignettes html is created properly

Author: Felix Cheung <felixcheung_m@hotmail.com>

Closes #16709 from felixcheung/rfilelicense.

(cherry picked from commit 385d7384)
Signed-off-by: Felix Cheung <felixcheung@apache.org>