Build on Xcode 11.4 and latest Swift (pod)

Change log:https://github.com/danielgindi/Charts/blob/master/CHANGELOG.md

Merged pull requests: Full github commit log

• Fix warnings on current code base #4321 (liuxuan30)
• Bugfix/legend offset double #4277 (danielgindi)
• Fix for #4274 string comparison issue in ChartData::getDataSetByLabel #4275 (PeterKaminski09)
• Restored correct velocity sampler #4273 (danielgindi)
• Bugfix/pie highlight #4272 (danielgindi)
• Call chartViewDidEndPanning on when *panning* is ended #4271 (danielgindi)
• labelXOffset = 10 is default for radar chart only #4270 (danielgindi)
• Use faster check for line whether it's inside drawing rect #4269 (danielgindi)
• Refactor/cleanup #4268 (danielgindi)
• address #4033 draw half pie chart more accurate #4266 (liuxuan30)
• Update README.md, added link to tutorial about Radar Charts. #4258 (DavidPiper94)
• Changes to fix Catalyst compatibility #4254 (CAPIStkidd)
• Platform separation #4178 (jjatie)
• introduce gracefully degrading abstractions for dark mode for ios and… #4171 (motocodeltd)
• Performed recommended localization and internationalization changes. #4162 (coltonlemmon)
• Use interpolation instead of '+' concatenation for problematic expression #4123 (Jumhyn)
• Allowing overriding for YAxisRenderer.drawYLabels #4089 (muclemente)
• move isDrawCirclesEnabled check further up in code to avoid creating … #4050 (xymtek)