adding pull request summarize into context menu (#6387)

Author: aiday-mar

package.json

@@ -2381,6 +2381,11 @@
 					"when": "view == pr:github && viewItem =~ /pullrequest|description/",
 					"group": "pullrequest@1"
 				},
+				{
+					"command": "issue.chatSummarizeIssue",
+					"when": "view == pr:github && viewItem =~ /pullrequest/ && github.copilot-chat.activated && config.githubPullRequests.experimental.chat",
+					"group": "pullrequest@2"
+				},
 				{
 					"command": "pr.openPullRequestOnGitHub",
 					"when": "view == pr:github && viewItem =~ /pullrequest|description/",