title: Upgrade to Webpack 5 breaking Storybook 5
body: <p>In process of upgrading a webpack 4/storybook 5 project to webpack 5 to hopefully take advantage of federated modules. I have regular <code>webpack --config webpack.config.js</code> building working atfer some struggle, but I can't seem to overcome this storybook config issue to get that working. there's not a lot in the storybook webpack.config.js - just some module rules for testing for less files and using the appropriate loaders. It seems the error I'm encountering is typical when upgrading webpack majors, as I've found a number of folks that encountered the same thing going from 3-4, but anything I've tried has failed so far. The specific stacktrace is:</p>
  
  <pre><code>Cannot read property 'tapAsync' of undefined
      at ExternalModuleFactoryPlugin.apply (/Users/tbullard/Workspace/unify/node_modules/webpack/lib/ExternalModuleFactoryPlugin.js:29:39)
      at compiler.hooks.compile.tap (/Users/tbullard/Workspace/unify/node_modules/webpack/lib/ExternalsPlugin.js:24:63)
      at SyncHook.eval [as call] (eval at create (/Users/tbullard/Workspace/unify/node_modules/tapable/lib/HookCodeFactory.js:19:10), &lt;anonymous&gt;:7:1)
      at SyncHook.lazyCompileHook (/Users/tbullard/Workspace/unify/node_modules/tapable/lib/Hook.js:154:20)
      at hooks.beforeCompile.callAsync.err (/Users/tbullard/Workspace/unify/node_modules/@storybook/core/node_modules/webpack/lib/Compiler.js:665:23)
      at _err0 (eval at create (/Users/tbullard/Workspace/unify/node_modules/tapable/lib/HookCodeFactory.js:33:10), &lt;anonymous&gt;:11:1)
      at compiler.inputFileSystem.readFile (/Users/tbullard/Workspace/unify/node_modules/@storybook/core/node_modules/webpack/lib/DllReferencePlugin.js:72:15)
      at process.nextTick (/Users/tbullard/Workspace/unify/node_modules/@storybook/core/node_modules/enhanced-resolve/lib/CachedInputFileSystem.js:85:15)
      at process._tickCallback (internal/process/next_tick.js:61:11)
  </code></pre>
  
  <p>Leads me to believe there's a plugin incompatibility ‍♂️ TIA!</p>