Create organization - build form

We need to build out the form that allows users to create a new organization.

Designs

#410343 (closed)

Implementation guide

1. Add app/assets/javascripts/organizations/new/components/app.vue
2. Add mount element to app/views/dashboard/organizations/new.html.haml
3. Export mounting function from app/assets/javascripts/organizations/new/index.js
4. Use GlFormFields to build the form
5. Use app/assets/javascripts/vue_shared/components/entity_select/group_select.vue to render the group selection
6. Use #417891 (closed) to create the new organization and redirect to the organization dashboard