Add back CSS class tags to challenge buttons (#101)

* Add back CSS class tags to challenge buttons

Author: ColdHeat

templates/challenges.html

@@ -47,7 +47,10 @@ <h3 x-text="category"></h3>
                   <div class="col-sm-6 col-md-4 col-lg-3 my-3">
                     <button
                         class="challenge-button btn btn-dark w-100 h-100"
-                        :class="c.solved_by_me ? 'challenge-solved' : ''"
+                        :class="[
+                          c.solved_by_me ? 'challenge-solved' : '',
+                          ...c.tags.map((tag) => `tag-${tag.value.replace(/ /g, '-')}`),
+                        ];"
                         :value="c.id" @click="loadChallenge(c.id)"
                     >