This commit changes the `engines` rules in the root `package.json` as
well as the `package.json` used when working on docs example to also
accept Node.js versions greater than v14. This aligns them with
`aio/package.json` and allows using Node.js v15 and v16 (current) for
local development in the `angular/angular` repo.
Related to #42367.
PR Close#42387