Build: fix hot reload for charts (#9400)

* Fix hot reload for charts

* Override tsc options for plugins

Plugins will sometimes have their own `tsconfig.json`, which will
interfere with the dev server config if configured inappropriately.

This change makes sure `tsc` (and `ts-loader`) always compiles to
`esnext` modules, so we don't get "Uncaught ReferenceError: exports
is not defined" error.

superset-frontend/tsconfig.json

@@ -25,8 +25,10 @@
   "include": [
     "./src/**/*",
     "./spec/**/*",
+    // include the source code of each plugin
     "./node_modules/*superset-ui*/**/src/**/*",
     "./node_modules/*superset-ui*/**/types/**/*",
+    // and the type defs of their dependencies
     "./node_modules/*superset-ui*/**/node_modules/**/*.d.ts"
   ]
 }