Implement index action. Repair destroy

app/views/user_exercise_feedbacks/index.html.slim

@@ -0,0 +1,19 @@
+h1 = UserExerciseFeedback.model_name.human(count: 2)
+
+.table-responsive
+  table.table
+    thead
+      tr
+        th colspan=2 = t('activerecord.attributes.user_exercise_feedback.user')
+        th = t('activerecord.attributes.user_exercise_feedback.exercise')
+        th colspan=2 = t('shared.actions')
+    tbody
+      - @uefs.each do |uef|
+        tr
+          td = uef.user.id
+          td = uef.user.name
+          td = link_to(uef.exercise.title, uef.exercise)
+          td = link_to(t('shared.show'), uef)
+          td = link_to(t('shared.destroy'), uef, data: {confirm: t('shared.confirm_destroy')}, method: :delete)
+
+= render('shared/pagination', collection: @uefs)