Release 3.2.1

• Run client finalizer in a Thread (if possible) for emergent Ruby 3.1 issue with net-http-persistent.
• Force running REXML in addition to Nokogiri by adding library keyword argument to parse_xml_bindings.
• Put documents on GH-pages.
• Improve TSV parsing and CSV tests.
• Set variable_names in solutions, which might not be the same as the actual variables used in the solutions.
• Client calling sequence example updates options usage (@white-gecko)