Add default success message (#128)

Author: EkaterinaVu

src/components/FlowForm.vue

@@ -46,6 +46,7 @@
               v-if="!submitted"
               v-html="language.formatString(language.pressEnter)">
             </a>
+            <p class="text-success" v-if="submitted">{{ language.successText }}</p>
           </slot>
         </div>
       </div>

src/models/LanguageModel.js

@@ -24,6 +24,7 @@ export default class LanguageModel {
     this.percentCompleted = ':percent% completed'
     this.invalidPrompt = 'Please fill out the field correctly'
     this.thankYouText = 'Thank you!'
+    this.successText = 'Your submission has been sent.'
     this.ariaOk = 'Press to continue'
     this.ariaRequired = 'This step is required'
     this.ariaPrev = 'Previous step'