Update to Chart.js 4 and Angular 15

[santam85]

• Updated to Chart.js v4
• Updated demo project to Angular 15
• Restyled doc website, removed legacy code

Fixes #1540

[jcompagner]

is it now really also on purpose that ng2-charts 4.1 can only be run on top of angular 15?
so 4.0.x is the latest supported version for angular 14?

I am not 100% sure how all that should work, because you kind of want to be compartible with angular 15 and support that, but not really force that you also have to use it, what is now the case because we do get:

Error: node_modules/ng2-charts/lib/base-chart.directive.d.ts:40:18 - error TS2707: Generic type 'ɵɵDirectiveDeclaration' requires between 6 and 8 type arguments.

40 static ɵdir: i0.ɵɵDirectiveDeclaration<BaseChartDirective<any, any, any>, "canvas[baseChart]", ["base-chart"], { "type": "type"; "legend": "legend"; "data": "data"; "options": "options"; "plugins": "plugins"; "labels": "labels"; "datasets": "datasets"; }, { "chartClick": "chartClick"; "chartHover": "chartHover"; }, never, never, false, never>;

and i guess that is an internal angular (ivy) thing

but as i said i do wonder how angular team thinks how this should work. or is it really what they do (with angular-material, ng-bootstrap, angular cdk) that they are now always also having those versions in sync with angular and they have also 14.x and 15.x package of all of them...

[santam85]

That's an oversight, I should have bumped the major version. The intention is that 4.0.x should work with Angular 14 AND 15, while v5 (to be created) only works of 15