Update Look and Feel of TreemapExport

Make these two changes to the treemap export:
1. JobHopper export is showing treechart as very difficult to read: Image is squished. Would be better if image was equally scaled so nothing is cutoff and the letters are similar to other items.
2. Header on the export should match the header in the webpage.

For Review, please have Lewis/Ram/Jeff/Allan/Lillian review the changes. Reach out them in slack and leave a note in the comments. Once someone reviews, make a comment in the ticket that this looks good and is approved. Another team member will then merge.

A good review will:
1. Ensure all bullets are done.
2. Ensure the code runs on your machine locally and works as expected.
3. Ensure that the tests run on your machine locally
4. There are no unresolved conflicts/errors with tests for the merge request.