v0.43.0

• Add experimental lookup code for comment references eventually
  destined to replace most of lib/src/markdown_processor.dart. Most
  of this work is disabled by default but does impact internal APIs.
  (#2637, #2634, #2630, #2622)
• Fix duplicate nullability suffix in some cases with markdown output.
  (#2632)
• Update analyzer requirement to 1.5.0 and fix/allow experimental
  features in 2.14. (#2625, #2618)
• Improvement to browser search, making browser find prioritize the
  main text area. (#2621)
• BREAKING CHANGE: hasDisplayedCategories replaced with
  hasCategoryNames. (#2614)
• Fix the public mixins link in the category sidebar. (#2613)
• Do not show late fields as 'read/write'. (#2608)
• Print version information when an exception is encountered. (#2607)
• A number of minor, internal cleanups.