feat(aio): enhance unit test experience with karma-jasmine-html-reporter

[wardbell]

See related PR 4567 in angular-cli

Please check if the PR fulfills these requirements

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

What kind of change does this PR introduce? (check one with "x")

[ ] Bugfix
[x] Feature
[ ] Code style update (formatting, local variables)
[ ] Refactoring (no functional changes, no api changes)
[ ] Build related changes
[ ] CI related changes
[ ] Other... Please describe:

What is the current behavior? (You can also link to an open issue here)

Karma browser window presents empty page. Have to dig around in console window to see results. Most people modify tests (with fit and xit) to focus on what they want.

What is the new behavior?
The karma-jasmine-html-report gives a more ergonomic experience. I really like it when I'm working on unit tests. So do my colleagues on the docs team where we have this setup.

It has no ill effects on CI nor on regular users of karma.

Does this PR introduce a breaking change? (check one with "x")

[ ] Yes
[x] No

If this PR contains a breaking change, please describe the impact and migration path for existing applications: ...

Other information:

[wardbell]

Closed by #14611

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