Add reactions to issues/PR and comments (#2856)

modules/setting/setting.go

@@ -256,6 +256,7 @@ var (
 		IssuePagingNum      int
 		RepoSearchPagingNum int
 		FeedMaxCommitNum    int
+		ReactionMaxUserNum  int
 		ThemeColorMetaTag   string
 		MaxDisplayFileSize  int64
 		ShowUserEmail       bool
@@ -279,6 +280,7 @@ var (
 		IssuePagingNum:      10,
 		RepoSearchPagingNum: 10,
 		FeedMaxCommitNum:    5,
+		ReactionMaxUserNum:  10,
 		ThemeColorMetaTag:   `#6cc644`,
 		MaxDisplayFileSize:  8388608,
 		Admin: struct {