Add simplified chart image for top of report

[colleenm]

• [x] For reports with too many clusters for legible bubble graphs, or for applications where populations want a simplified view, we should show a less interactive chart.

• [x] For now, this should be the default view. Chart should use updated color scheme from #116 (ignore colors in mocks below). Margins and text sizes in the mocks below are final.

• [x] 1. Minimum viable version: bar chart with topics & descriptions

• [x] - Bar graph shows the topic title and (brief) description for each topic. Title and description should each be a maximum of two lines (add ellipsis if it continues past two lines).

• [x] - Bars should include text showing number of claims in the bar (bold white text, left-aligned)

• [x] - Bar chart should have a single, vertical, unlabeled axis (no horizontal axis)

• [x] 2. Target version: hover behavior
• [x] When any part of a topic is hovered over (title, description, or bar area):
• [x] - that entire row of the bar graph should be highlighted in a 10% opacity version of that bar's color
• [x] - the text "Click to view topic" should appear in small italic text below the bar. To ensure there is room for this, each topic's text should have a min-height set (see mock)

• [ ] 3. Nice-to-have: subtopics on hover
• [ ] On hover, a topic should expand to include a list of subtopics in that cluster.
• [ ] - "Subtopics" heading should show the total number of subtopics
• [ ] - Subtopics should be limited to one line of text (elided)
• [ ] - Subtopics should be delimited by commas and three extra spaces, for legibility

[colleenm]

@lightningorb I'm hoping we can use an existing bar chart library for a lot of this; if you find one that comes close to supporting these designs but isn't quite there, lmk and I can try to revise designs to make it work

[colleenm]

Calling this done! We can revisit subtopics on hover if subtopics aren't discoverable enough via sidebar and per-topic graphs, but I don't expect that to be the case