New client party tutorial (#8968)

* Adjusted intro tutorial

* Added images to create party modal

* Fixed shared button styles

* Added method to start a party

* various style fixes

website/client/components/challenges/groupChallenges.vue

@@ -5,7 +5,7 @@ div
     .col-12.text-center
       .svg-icon.challenge-icon(v-html="icons.challengeIcon")
       h4(v-once) {{ $t('haveNoChallenges') }}
-      p(v-once) {{ $t('challengeDescription') }}
+      p(v-once) {{ $t('challengeDetails') }}
   router-link.title(:to="{ name: 'challenge', params: { challengeId: challenge._id } }", v-for='challenge in challenges',:key='challenge._id')
     .col-12.challenge-item
       .row