Add help-email shortcode and holiday update news item

Primarily adds the holiday hours announcement, but also...

• adds a {{< help-email >}} shortcode that creates a mailto link
• changes vramX constraint description to include "at least", e.g. "Contains a GPU with at least 80 GB VRAM"
• edits "Contact Us" to note office hours hiatus
• Adds a convenience Docker script for using hugo new