Add support for charts to the extension API

Created by: felixfbecker

Adds support for charts in the extension API. It basically exposes a declarative, object literal API over recharts. I'm not 100% sure about all API aspects but am happy enough with this version to ship it for experimentation

Example usages:

• Line charts: https://github.com/sourcegraph/sourcegraph-search-insights
• Pie charts: https://github.com/codecov/sourcegraph-codecov/pull/52

Testing strategy: Storybooks.

Closes #10018