Add PDF for printing with Flyeralarm

contribute/how/promote/material/stickers.mdwn

@@ -4,4 +4,8 @@ These stickers may help you [[promote Tails|contribute/how/promote]].
 They are published under the same license as the [[Tails
 logo|contribute/how/promote/material/logo]].
 
+[Flyeralarm](https://www.flyeralarm.com/) has good prices, ships all
+around Europe, and we already have a [[PDF|tails-sticker-flyeralarm.pdf]]
+to print 5 cm round stickers with them.
+
 [[!map pages="contribute/how/promote/material/stickers/*"]]