Add CHART.JS v4 compatibility

[stockiNail]

Fix #164

• solve a couple of TS types issues.
• chartjs-adapter-date-fns not compatible with CHART-JS 4 yet.
• chart-plugin-datalabels not compatible with CHART-JS 4 yet

[stockiNail]

@kurkle I'm going on tomorrow. About requireVersion function, it didn't work with version 4.0.1. I have copied the implementation of annotation plugin, so they are aligned.

[kurkle]

I think it only needs updated date-fns adapter and should be fine.

[stockiNail]

I have an issue importing color functions from the helpers of Chartjs in the types test. I wrote it in slack.
Sounds an issue of version 4 but not sure

[stockiNail]

I think it only needs updated date-fns adapter and should be fine.

having a look to the error, it seems more related to datalabels. Date-fns adapter version updated to 2.0.1.

[stockiNail]

I have an issue importing color functions from the helpers of Chartjs in the types test. I wrote it in slack.
Sounds an issue of version 4 but not sure

I have changed tsconfig and now it's working

[stockiNail]

@kurkle do you know why date-fns is needed? I don't see any place where it's used (if I'm not wrong)