fix: add v prefix to release-drafter's tag template (#497)

In order to make tags created by the release-drafter compatible with Go modules, 
tags have to begin with `v` prefix.

Author: czeslavo

.github/release-drafter.yml

@@ -1,5 +1,5 @@
 name-template: "v$NEXT_PATCH_VERSION 🌈"
-tag-template: "$NEXT_PATCH_VERSION"
+tag-template: "v$NEXT_PATCH_VERSION"
 categories:
   - title: "🚀 Features"
     labels: