Document how to download the latest build artifacts

## What does this MR do?

Document how to download the latest build artifacts.

Closes gitlab-org/gitlab-ce#22273

See merge request !6401

[ci skip]

Update GitHub importer documentation  to reflect current importer state

## What does this MR do?

Update the Github importer documentation to reflect the current importer state.

## What are the relevant issue numbers?

https://gitlab.com/gitlab-org/gitlab-ee/issues/904

## Does this MR meet the acceptance criteria?

- [X] [Documentation created/updated](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/doc/development/doc_styleguide.md)


See merge request !5987

improve wording on build and push images using GitLab CI docs

## What does this MR do?

Improve wording on build and push images using GitLab CI docs

## Are there points in the code the reviewer needs to double check?

No

## Why was this MR needed?

Poor wording

## Does this MR meet the acceptance criteria?

- [ ] [CHANGELOG](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CHANGELOG) entry added
- [X] [Documentation created/updated](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/doc/development/doc_styleguide.md)
- [ ] API support added
- Tests
  - [ ] Added for this feature/bug
  - [ ] All builds are passing
- [ ] Conform by the [style guides](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CONTRIBUTING.md#style-guides)
- [X] Branch has no merge conflicts with `master` (if you do - rebase it please)
- [ ] [Squashed related commits together](https://git-scm.com/book/en/Git-Tools-Rewriting-History#Squashing-Commits)

See merge request !6001