Chartjs-Decimal in x-axis

For the y-axis, using the stepSize variable of the ticks option does the trick. Doing the same for the x-axis is a little more complex but not impossible.

The first issue is that your x-axis labels are at integer intervals so the chart has nowhere to position the decimal values than at the closest integer. This can be fixed by specifying all the values in the desired intervals (ie: 0.1, 0.2,…,3.0) in the labels.
Then, making use of the autoSkip and maxTicksLimit, you can hide the labels not needed and so create the chart seen in your image, but with the points in the correct position.

I made a working version of this using your code in this fiddle. Hope this helps!