Improve bundling/minification recommendations

[welingtonms]

Solves lit.dev's #1161

• Inform developers that the terser configuration is targeting the docs static site generation
• Refer to the Lit site for best practices on publishing Web Components and applications that include them.

[google-cla[bot]]

Thanks for your pull request! It looks like this may be your first contribution to a Google open source project. Before we can look at your pull request, you'll need to sign a Contributor License Agreement (CLA).

View this failed invocation of the CLA check for more information.

For the most up to date status, view the checks section at the bottom of the pull request.

[AndrewJakubowicz]

Hi! Thanks for the pull request! The changes look great to me!

Unfortunately, the starter kit files are copied out of the main lit/lit repo from the packages subdirectory. Would you be able to submit this PR to https://github.com/lit/lit modifying the files there: https://github.com/lit/lit/tree/main/packages/lit-starter-js

I think if this change is submitted here, then there is a risk in the future of the original README undoing your work.

[welingtonms]

Hi, @AndrewJakubowicz, thanks for letting me know about that!

Just opened the PR there.