add help content for static page
Since the re-design there is now only one static page. (And possibly "Feedback".) Lift the content from the document cited in #11 (closed) and add some basic styling for the page.
Static page content and titles are now defined in ES6 modules under src/static for convenience of editing. The Static component is re-worked to accept a page name corresponding to the module name under src/static.
Update the sidebar to link to the only static page we currently have.
Closes #11 (closed)