Add a formatter to tickAmount

[gustavi]

It's a cool feature in Chart.js; you can hook in the function that draw ticks and draw them a specific condition. For example I would like to draw values every 25 but I would like to include "1".

Code sample;

tickAmount: {
  formatter: function(val) {
    if ((val === 1) || (val % 25 === 0)) return val;
  }
}