PHPMailer 6.1.8

This is a maintenance release.

• Mark ext-hash as required in composer.json. This has long been required, but now it will cause an error at install time rather than runtime, making it easier to diagnose
• Make file upload examples safer
• Update links to SMTP testing servers
• Avoid errors when set_time_limit is disabled (you need better hosting!)
• Allow overriding auth settings for local tests; makes it easy to run tests using HELO
• Recover gracefully from errors during keepalive sessions
• Add AVIF MIME type mapping
• Prevent duplicate To headers in BCC-only messages when using mail()
• Avoid file function problems when attaching files from Windows UNC paths
• Improve German, Bahasa Indonesian, Filipino translations
• Add Javascript-based example
• Increased test coverage