[Feature] Support steps

[congnguyen91]

• It means that we have two limitations (like: min(0) & max(20).

• Case 1: When user move the tracking point with step(5). When user drag > 7, 8. It can set automatically to 10.
• Case 2: We have a custom steps like an array: [1, 2, 5, 10, 15]. Determine the nearest value on endTracking to set the final tracking point.