Added support for the Angular compiler.

The Angular compiler looks for the main field using a few fields in the package.json. The order it uses is:
- es2020
- es2015
- browser
- module
- main

The first entry the Angular compiler would find before this change was the 'main' entry point. This is however compiled as `common js` and Angular is looking for an `esm` so it would complain (it would still work though). Adding `es2020` as an entry point fixes this problem.

Author: jeroen1602

package.json

@@ -7,6 +7,7 @@
     "url": "https://github.com/apexcharts/apexcharts.js.git"
   },
   "main": "dist/apexcharts.common.js",
+  "es2020": "dist/apexcharts.esm.js",
   "unpkg": "dist/apexcharts.js",
   "jsdelivr": "dist/apexcharts.js",
   "typings": "types/apexcharts.d.ts",