Update links in connection-api docs
Update links in connection-api docs

Fixes a few links in the connection-api docs to point towards more context appropriate pages. "Learn more about Repositories" should navigate to `working-with-repository.md` and "Learn more about custom repositories" should navigate to `custom-repository.md`.
typeorm/typeorm,typeorm/typeorm,typeorm/typeorm,gintsgints/typeorm,gintsgints/typeorm