`express-serve-static-core` and `serve-static` should be an explicit (optional) dependencies if their types are part of export

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### Bug report



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### Actual Behavior



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With Webpack-dev-server@4.9.0, typescript@4.7.2, and yarn@3.2.1



```sh

$ yarn tsc



.yarn/__virtual__/webpack-dev-server-virtual-ca9edd4c98/2/.yarn/berry/cache/webpack-dev-server-npm-4.9.0-35850a5f47-8.zip/node_modules/webpack-dev-server/types/lib/Server.d.ts:3197:18 - error TS2307: Cannot find module 'express-serve-static-core' or its corresponding type declarations.



3197           import("express-serve-static-core").ParamsDictionary,

                      ~~~~~~~~~~~~~~~~~~~~~~~~~~~



.yarn/__virtual__/webpack-dev-server-virtual-ca9edd4c98/2/.yarn/berry/cache/webpack-dev-server-npm-4.9.0-35850a5f47-8.zip/node_modules/webpack-dev-server/types/lib/Server.d.ts:3428:18 - error TS2307: Cannot find module 'express-serve-static-core' or its corresponding type declarations.



3428           import("express-serve-static-core").ParamsDictionary,

                      ~~~~~~~~~~~~~~~~~~~~~~~~~~~



.yarn/__virtual__/webpack-dev-server-virtual-ca9edd4c98/2/.yarn/berry/cache/webpack-dev-server-npm-4.9.0-35850a5f47-8.zip/node_modules/webpack-dev-server/types/lib/Server.d.ts:3523:34 - error TS2307: Cannot find module 'serve-static' or its corresponding type declarations.



3523 type ServeStaticOptions = import("serve-static").ServeStaticOptions;

                                      ~~~~~~~~~~~~~~



.yarn/__virtual__/webpack-dev-server-virtual-ca9edd4c98/2/.yarn/berry/cache/webpack-dev-server-npm-4.9.0-35850a5f47-8.zip/node_modules/webpack-dev-server/types/lib/Server.d.ts:3556:14 - error TS2307: Cannot find module 'serve-static' or its corresponding type declarations.



3556     | import("serve-static").ServeStaticOptions<import("http").ServerResponse>

                  ~~~~~~~~~~~~~~



[9:29:45 AM] Found 4 errors. Watching for file changes.

```



### Expected Behavior



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tsc should compile without error. `@types/express-serve-static-core` and `@types/serve-static` should be an explicit (optional) dependencies if their types are part of export.



### How Do We Reproduce?



I'll try and create a repro repo later today.



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### Please paste the results of `npx webpack-cli info` here, and mention other relevant information

[]