Documentation update: Domain Verification

Document: Verify a domain for your organization 873871234.html

Under "Domain verification considerations" and in the context of the HTTPs verification method, it would be beneficial to:

• Include the user agent information of the client that we use to verify domains on the verification page.
• Include information as to how to troubleshoot issues with HTTPs domain verification - checking the "atlassian-domain-verification.html" via a browser, etc.

The reason being is that more and more customers are deploying Web Application Firewalls(WAF) and we may need to be whitelisted. This information would be useful in helping customers identify issues with domain verification, esp. when "atlassian-domain-verification.html" is accessible, but the domain still can't be verified.