Clarify issue link number

Author: niccokunzmann

.github/PULL_REQUEST_TEMPLATE.md

@@ -1,4 +1,6 @@
-Issue for this pull request:   <!-- paste a link or write #1 for issue number 1 -->
+Issue for this pull request:   <!-- paste a link or write #1 for issue number 1      ⬇
+                                    https://github.com/CoderDojoPotsdam/intro/issues/1
+                                    #2 for issue number 2, ... -->
 
 **Problem to solve:**