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

josephperrott/material2,josephperrott/material2,crisbeto/material2,josephperrott/material2,angular/components,josephperrott/material2,angular/components,josephperrott/material2,crisbeto/material2,crisbeto/material2,angular/components,angular/components,crisbeto/material2