docs: add use Rspack to build performance guide

[chenjiahan]

This PR adds the "use Rspack" guide to the build performance document.

Using Rspack can be a pragmatic option for Webpack users. If the user has already tried to optimize the build performance of the webpack application and has not achieved the expected results, then using Rspack would be a good choice.

Feel free to close this if this is inappropriate for webpack documentation ❤️

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[chenjiahan]

@alexander-akait Can you review this PR? Thanks! ❤️