Redirect users to "awaiting approval" message on register (#231)

Ref #81 - this implements a "your request has been sent" message

 ![image](/attachments/61dc3f5e-2706-46f9-a1ca-4efe3f526ff3)

Co-authored-by: FloatingGhost <hannah@coffee-and-dreams.uk>
Reviewed-on: https://akkoma.dev/AkkomaGang/pleroma-fe/pulls/231

src/components/registration/registration.vue

@@ -177,6 +177,7 @@
             <div
               v-if="accountApprovalRequired"
               class="form-group"
+              :class="{ 'form-group--error': v$.user.reason.$error }"
             >
               <label
                 class="form--label"