build: add subpath export for fesm2020 bundles of components-examples

Adds a subpath export for the `fesm2020` folder of the internal
`@angular/components-examples` package. This subpath is needed so that
Webpack can generate lazy-loadable chunks for all examples in the
documentation app.

Author: devversion

src/components-examples/package.json

@@ -13,6 +13,9 @@
     "material design",
     "components"
   ],
+  "exports": {
+    "./fesm2020": {"default": "./fesm2020"}
+  },
   "license": "MIT",
   "bugs": {
     "url": "https://github.com/angular/components/issues"