BarChart: highlight x-axis value when tapped

## What did you expect to happen?
I need to handle action on x-axis value and highlight x-axis value

## What happened instead?
Touch in x-axis value will highlight the bar, not the x-axis value
## DGCharts Environment

**DGCharts version/Branch/Commit Number:** 5.1.0
**Xcode version:** 14.0
**Swift version:** 5.0
**Platform(s) running DGCharts:** iOS
**macOS version running Xcode:** Monterey 12.6.3

## Demo Project

ℹ Please link to or upload a project we can download that reproduces the issue.

Start by reproducing the tap behavior in a BarChart on iOS with DGCharts 5.1.0, then trace how touches on x-axis values are handled versus bar selection. Done means an x-axis tap triggers the requested action and highlights the x-axis value rather than the bar.

Written by the indexing model from the issue text.