recognise BitBucket hosts by WWW-Authenticate header

Tested with https://bitbucket.hl7.org

Author: hickford

src/shared/Atlassian.Bitbucket/BitbucketHostProvider.cs

@@ -1,5 +1,6 @@
 using System;
 using System.Collections.Generic;
+using System.Linq;
 using System.Net.Http;
 using System.Threading.Tasks;
 using Atlassian.Bitbucket.Cloud;
@@ -43,6 +44,10 @@ public bool IsSupported(InputArguments input)
                 return false;
             }
 
+            if (input.WwwAuth.Any(x => x.Contains("realm=\"Atlassian Bitbucket\"")))
+                return true;
+            }
+
             // Split port number and hostname from host input argument
             if (!input.TryGetHostAndPort(out string hostName, out _))
             {