v4.22.1p4

• Apply Pull-Request #84 (issue #83) for setting the value of softorhard in Sisimai::SMTP::Error.soft_or_hard method. Thanks to @lunatyq.
• Fix a wrong value assingment, and code for Performance/StartWith reported from Rubocop in Sisimai::Bite::Email::GSuite.
• Update codes about Lint/AssignmentInCondition, Style/Next, Style/EmptyElse, Style/UselessAssignment, and others reported from Rubocop.
• Fix code for Performance/Casecmp, Performance/LstripRstrip in Sisimai::MIME.
• Update code for Style/SymbolProc in Sisimai::Message::Email.
• Support parsing JSON object from SendGrid Event Webhook.
• Suuport "event": "spamreport" via Feedback Loop on SendGrid Event Webhook.
• Implement Sisimai::Address.is_undisclosed method.
• Import Pull-Request #237: Support parsing bounce mail from GoDaddy.
• Fix bug for setting the value of date in Sisimai::Bite::Email::Postfix.