Fixed final typings/removed WelcomeJumbotron

frontend/src/components/WelcomeJumbotron.vue

...nd/src/components/feedback_list/FeedbackSearchOptions.vue

frontend/src/pages/reviewer/ReviewerStartPage.vue

frontend/src/pages/tutor/TutorStartPage.vue

frontend/src/store/modules/authentication.ts

frontend/src/store/modules/feedback_list/feedback-table.ts

frontend/src/store/modules/submission-notes.ts

frontend/src/store/modules/subscriptions.ts

frontend/src/store/mutations.ts

frontend/src/store/store.ts