Add Webpack support with example & updated docs for it.

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## Description

- Who wants the functionality
- This feature would be beneficiary for developers who use webpack for the build ecosystem and want to use Lit.
- What it is they want
- Webpack official support for lit to drive dev, CICD & production workflow
- Webpack examples for above all & starter kit also
- Detailed docs about above all for easy and clear understanding like rollup one.
- Why they want it
- For using webpack with lit, developers need documentation and example of lit.
- Functional description of task/subtask
- Provide documentation of using webpack with lit
- Playground or github example demonstrating support of lit with webpack.

**Pros**

- Webpack users can adapt Lit in one click.
- It will help those developers who's manager or company allowed only webpack.
- New developers can compare different build system and select as per their need.

## Acceptance criteria

- Starter kit showing demo of using lit with webpack
- Documentation in lit.dev

Start by reviewing the existing Rollup documentation on lit.dev and the project's current starter-kit or example structure. Add a Webpack starter kit or example covering development, CI/CD, and production workflows, then document it on lit.dev. Done means the example works and the documentation clearly explains the setup.

Written by the indexing model from the issue text.