Fetch Public and TWKN timelines when viewed.

...lic_and_external_timeline/public_and_external_timeline.js

src/components/public_timeline/public_timeline.js

src/modules/api.js

src/modules/users.js

.../backend_interactor_service/backend_interactor_service.js

src/services/timeline_fetcher/timeline_fetcher.service.js