Add lazy load example

I wrote an example component able to lazy load languages to avoid bundling everything: https://codesandbox.io/s/lazy-load-prism-react-renderer-2g7qhh

Doesn’t support language aliases, only the language names used in the filename (e.g. `bash`, but not `shell` or `sh`, since the file is called `prism-bash.js`)

You might want to link it (or a fork you control) from the readme.

Review the linked CodeSandbox lazy-loading example and locate the repository README. Decide whether the existing example or a maintained fork should be linked, preserving the note about language aliases. Done means the README contains the appropriate link and accurately describes the example.

Written by the indexing model from the issue text.