Support browsers from before 2020

As reported in #2825, #2826 and #3051, almost everything works in older browsers. This setting here prevented me from updating and I think it is an obvious enhancement to not restrict to browsers from 2020+. There should not be any measurable downsides of this change since es6 and es2020 are pretty similar with only minor differences.

Author: L3P3

tsconfig.json

@@ -1,6 +1,6 @@
 {
   "compilerOptions": {
-    "target": "es2020",
+    "target": "es6",
     "module": "commonjs",
     "moduleResolution": "node",
     "strict": true,