feat: add @rspack/core as an optional peer dependency

[chenjiahan]

Background

Rspack is a fast Rust-based web bundler and it is compatible with the architecture and ecosystem of webpack.

The html-webpack-plugin can be used with Rspack, but users will get a peer dependency warning:

 WARN  Issues with peer dependencies found
.
 └─┬ html-webpack-plugin 5.5.3
    └── ✕ missing peer webpack@^5.20.0

Description

This PR adds @rspack/core as an optional peer dependency, and make webpack as an optional peer dependency too.

Related issues

• Add @rspack/core to the peer dependencies of html-webpack-plugin and react-refresh-webpack-plugin web-infra-dev/rspack#4537
• Add webpack as optional peer dependency webpack/webpack-dev-server#4776