Docs examples of type `i18n` need a slightly modified version of
`polyfills.ts` that imports `@angular/localize/init`. Previously, this
file was not included in `i18n` example projects for two reasons:
- While the file was included in the `i18n` boilerplate files (at
`aio/tools/examples/shared/boilerplate/i18n/`), it was not included in
the boilerplate file list in `example-boilerplate.js`.
- The file was in the wrong location: It was located at the project root
instead of inside the `src/` directory.
This commit addresses the above issues (i.e. adds the file to the
boilerplate file list for `i18n` projects and moves the file inside the
`src/` directory).
PR Close#38173
