Send emails via Gmail with support for attachments, HTML formatting, and send-as aliases.

• Requires recipient email(s), subject, and body text; supports CC, BCC, and optional sender address for send-as aliases
• Handles file attachments up to 25MB total, with multiple files supported via repeated --attach flags
• Supports both plain text and HTML email bodies; HTML fragments do not require wrapper tags
• Includes --dry-run flag to preview the request before sending, and automatic RFC 5322 formatting and MIME encoding