- Update search-result page URL pattern and selectors for search-result
  entries.
- Be less eager in monitoring DOM change; do this only when the page
  could possibly be a search-result page as determined by URL.
- Update a test case due to change in canonical URL field in output.

- Don't use a separate code path for scraping the current page; use the
  same scrape() function for both search results and current page
- Asyncify the network requests
- Clean up any HTML entities in the API-returned text fields (title,
  abstract, etc.)
- More reliable way to extract the "id" of individual preprints: it's
  the last segment in the path
- Overall reduction of code duplication
- Update and add tests

The API endpoint may respond with HTML (for human consumption) depending
on a variety of factors. To prevent this, explicitly add "Accept:"
header to the request.

- The PDF attachment is named "Preprint PDF"
- Use `ZU.cleanAuthor()` to normalize author name in consistency with
  other translators

The domain osf.io is now the host of the discipline-specific projects,
so we only need to match that.