BarChart bottom legend issue

## What did you do?

Fill barchart entries with simple dates (10-02-2021, 10-01-2021, 25-12-2020) and set an AxisFormatter to set the string value for the month.

## What did you expect to happen?

Set the bars with their month.

## What happened instead?

When the dates aren't ordered (e.g. feb-21, jan-21, dec-20, nov-20) the "stringForValue" function in the AxisFormatter doesn't recognize the correct month, instead set all the missing values for the months and repeats that method for at least 4 more times, sometimes 5 times.

## Charts Environment

**Xcode version: 12.5
**Swift version: 5.3
**Platform(s) running Charts: iOS 14.3

## Swift File that sets the barDataSet

let barEntries = (0.. BarChartDataEntry in
let dateIndex = data[i].date.index(data[i].date.startIndex, offsetBy: 10)
let strDate = String(data[i].date[.. String {
return getMonth(Int(value))
}

private func getMonth(_ month: Int) -> String {
switch month {
case 12:
return "Dic."
case 11:
return "Nov."
case 10:
return "Oct."
case 9:
return "Sept."
case 8:
return "Ago."
case 7:
return "Jul."
case 6:
return "Jun."
case 5:
return "May."
case 4:
return "Abr."
case 3:
return "Mar."
case 2:
return "Feb."
default:
return "Ene."
}
}

Start by reproducing the issue with the unordered dates and the shown BarChartDataEntry values, then inspect how AxisFormatter.stringForValue is called for the bar chart axis. Done means each bar receives the correct month label without repeated missing values or incorrect formatter results.

Written by the indexing model from the issue text.