Update meta.yml

Author: rajibrpf

en/meta.yml

@@ -2,6 +2,7 @@
 title: Make a face
 hero_image: images/banner.png
 description: Design and draw a face or mask using geometric shapes
+pdf: resources/rpfi-make-a-face.pdf
 meta_title: Python coding projects for kids and teens | Make a face
 meta_description: Learn Python with the Raspberry Pi Foundation's coding projects for kids and teens. Write Python code to draw a face or mask using geometric shapes.
 version: 4
@@ -29,4 +30,4 @@ steps:
     completion:
       - external
   - title: Challenge
-    challenge: true
+    challenge: true