add changes field in to GitHub PullRequestPayload.

github/payload.go

@@ -3544,6 +3544,15 @@ type PublicPayload struct {
 	} `json:"sender"`
 }
 
+type PullRequestChanges struct {
+	Title *struct {
+		From string `json:"from"`
+	} `json:"title"`
+	Body *struct {
+		From string `json:"from"`
+	} `json:"body"`
+}
+
 // PullRequestPayload contains the information for GitHub's pull_request hook event
 type PullRequestPayload struct {
 	Action      string `json:"action"`
@@ -4006,6 +4015,7 @@ type PullRequestPayload struct {
 		Type              string `json:"type"`
 		SiteAdmin         bool   `json:"site_admin"`
 	} `json:"sender"`
+	Changes           *PullRequestChanges `json:"changes"`
 	Assignee          *Assignee           `json:"assignee"`
 	RequestedReviewer *Assignee           `json:"requested_reviewer"`
 	RequestedTeam     struct {