updated welcome email

[skull8888888]

[!IMPORTANT] Updated WelcomeEmail content and styling to provide detailed information and links to documentation.

• Content Update:
  • Revised welcome message in WelcomeEmail to include more detailed information about Laminar's features and open-source nature.
  • Added links to specific documentation sections for tracing, evaluations, labels, and datasets.
• Styling:
  • Updated font family to 'Inter' in text style.
  • Added new styles: container, heading, link, signature, role, bulletList, and bulletPoint for improved layout and readability.

^{This description was created by for 9d3943b40279160c3f9a21108db0f0eb920f2e01. It will automatically update as commits are pushed.}