Show loader in docs app

[Narretz]

What kind of change does this PR introduce? (Bug fix, feature, docs update, ...)
update to the docs app

What is the current behavior? (You can also link to an open issue here)
No loader is displayed when changing views in the docs

Does this PR introduce a breaking change?
No

Please check if the PR fulfills these requirements

• The commit message follows our guidelines: https://github.com/angular/angular.js/blob/master/CONTRIBUTING.md#commit-message-format
• Tests for the changes have been added (for bug fixes / features)
• [ ] Docs have been added / updated (for bug fixes / features)

[googlebot]

We found a Contributor License Agreement for you (the sender of this pull request) and all commit authors, but as best as we can tell these commits were authored by someone else. If that's the case, please add them to this pull request and have them confirm that they're okay with these commits being contributed to Google. If we're mistaken and you did author these commits, just reply here to confirm.

[googlebot]

We found a Contributor License Agreement for you (the sender of this pull request) and all commit authors, but as best as we can tell these commits were authored by someone else. If that's the case, please add them to this pull request and have them confirm that they're okay with these commits being contributed to Google. If we're mistaken and you did author these commits, just reply here to confirm.

[googlebot]

CLAs look good, thanks!

[googlebot]

CLAs look good, thanks!

[petebacondarwin]

LGTM