J8 Notation

  [J8 Strings]   json-string        "hi"
                 json-escape        \"  \\  \u1234
                 surrogate-pair     \ud83e\udd26
                 j8-escape          \'  \u{1f926}  \yff
                 u-prefix           u'hi'
                 b-prefix           b'hi'
                 no-prefix          'hi'
  [J8 Lines]     unquoted-line
  [JSON8]        json8-num          json8-str
               X json8-list       X json8-dict
                 json8-comment
  [TSV8]         column-attrs       column-types
