Added data-viz nav item

[jimmynotjim]

Added the datavisualization item to the main navigtaion

Changes

• Uncommented hidden data-viz nav item in the main nav.

Testing

• Start the server and check the main nav

Review

• @Scotchester
• @caheberer

Preview this PR without the whitespace changes

Screenshots

Notes

• Fixes #453
• There is currently zero content on the page that was already set up. Not sure who's responsible for that.

Todos

• Add content to the new page.
• Fill out the Sidebar nav as child pages are added.

Checklist

• [x] Changes are limited to a single goal (no scope creep)
• [x] Code can be automatically merged (no conflicts)
• [x] Code follows the standards laid out in the front end playbook
• [x] Passes all existing automated tests
• [x] New functions include new tests
• [x] New functions are documented (with a description, list of inputs, and expected output)
• [x] Placeholder code is flagged
• [x] Visually tested in supported browsers and devices
• [x] Project documentation has been updated (including the "Unreleased" section of the CHANGELOG)

[Scotchester]

Uhhh, I'm going to revert this, because the page has no content yet.

[caheberer]

@Scotchester is this a large concern? If adding this nav item, or other small tweaks like this, allows someone to pick up the work from here, is there a reason that we can't have a blank page for a bit? I'm thinking any tiny bit of forward progress is better than none. But definitely interested in hearing your thoughts.

[Scotchester]

I'm not sure it's a large concern, but it doesn't feel right to be pointing to a page that is literally blank, other than the title.

Also, having the page in the navigation is not a prerequisite for being able to work on it. Since the file exists in the repo, anyone can navigate to /data-visualization/data-visualization.html and see the page.

[caheberer]

Gotchya. Makes sense.

[jimmynotjim]

The nav item was already there too, I just un-hid it.