Add API for showing and hidding axis. Fixes #1520

[missingdays]

Add new API for showing and hidding x and y axis

chart.axis.isXShown(); // will return true, if x axis is visible, false otherwise
chart.axis.isYShown(); // will return true, if y axus is visible, false otherwise

chart.axis.isXShown(true) // will make x axis visible
chart.axis.isXShown(false); // will make x axis hidden
chart.axis.isYShown(true) // will make y axis visible
chart.axis.isYShown(false); // will make y axis hidden

[codecov-io]

Current coverage is 63.85%

Merging #1760 into dev will increase coverage by 0.11%

@@                dev      #1760   diff @@
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  Files             1          1          
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+ Hits           2820       2834    +14   
  Misses         1604       1604          
  Partials          0          0          

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[skout90]

love it!🌹