Add Technical Support Guide & update issue templates

[corinagum]

Fixes #3535

Changelog Entry

• Resolves #3535. Add Technical Support Guide for guidance on troubleshooting information and navigating the Web Chat repository, by @corinagum, in PR #3645

Description

• Provide a Technical Support Guide for both customers and support engineers to diagnose problems without needing to file a new issue.
• Update the issue templates

• [ ] I have added tests and executed them locally
• I have updated CHANGELOG.md
• I have updated documentation

Review Checklist

This section is for contributors to review your work.

• Accessibility reviewed (tab order, content readability, alt text, color contrast)
• Browser and platform compatibilities reviewed
• CSS styles reviewed (minimal rules, no z-index)
• Documents reviewed (docs, samples, live demo)
• Internationalization reviewed (strings, unit formatting)
• package.json and package-lock.json reviewed
• Security reviewed (no data URIs, check for nonce leak)
• Tests reviewed (coverage, legitimacy)