setup eslint to also lint vue templates

frontend/.eslintrc.js

frontend/src/App.vue

frontend/src/components/AutoLogout.vue

frontend/src/components/BaseLayout.vue

frontend/src/components/CorrectionStatistics.vue

frontend/src/components/GDPRNotice.vue

frontend/src/components/LabelStatistics.vue

frontend/src/components/PasswordChangeDialog.vue

frontend/src/components/RegisterDialog.vue

frontend/src/components/SubmissionTests.vue

frontend/src/components/UserOptions.vue

frontend/src/components/export/DataExport.vue

frontend/src/components/export/ExportDialog.vue

frontend/src/components/export/InstanceExport.vue

frontend/src/components/feedback_labels/FeedbackLabel.vue

...tend/src/components/feedback_labels/FeedbackLabelForm.vue

...d/src/components/feedback_labels/FeedbackLabelUpdater.vue

...end/src/components/feedback_labels/FeedbackLabelsList.vue

frontend/src/components/feedback_labels/LabelSelector.vue

...end/src/components/feedback_list/FeedbackListHelpCard.vue