New Issue ?body= query (#5851)

* New Issue ?body= query

* Override issue template with body query

* Add documentation for issue body query

routers/repo/issue.go

@@ -374,6 +374,8 @@ func NewIssue(ctx *context.Context) {
 	ctx.Data["RequireSimpleMDE"] = true
 	ctx.Data["RequireTribute"] = true
 	ctx.Data["PullRequestWorkInProgressPrefixes"] = setting.Repository.PullRequest.WorkInProgressPrefixes
+	body := ctx.Query("body")
+	ctx.Data["BodyQuery"] = body
 
 	milestoneID := ctx.QueryInt64("milestone")
 	milestone, err := models.GetMilestoneByID(milestoneID)