Support binding of left-click and right-click

left-click and right-click are respectively bound to "ignore" and
"toggle" (after implicitly moving the cursor) by default.

Close #1130

src/options.go

@@ -430,6 +430,10 @@ func parseKeyChords(str string, message string) map[int]string {
 			chord = tui.SLeft
 		case "shift-right":
 			chord = tui.SRight
+		case "left-click":
+			chord = tui.LeftClick
+		case "right-click":
+			chord = tui.RightClick
 		case "double-click":
 			chord = tui.DoubleClick
 		case "f10":