Copy invalid-resolve-alias as it is being linked in the codebase

errors/invalid-resolve-alias.md

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+# Invalid webpack resolve alias
+
+#### Why This Error Occurred
+
+When overriding `config.resolve.alias` incorrectly in `next.config.js` webpack will throw an error because private-next-pages is not defined.
+
+#### Possible Ways to Fix It
+
+This is not a bug in Next.js, it's related to the user adding a custom webpack(config) config to next.config.js and overriding internals by not applying Next.js' aliases. Solution would be:
+
+```js
+webpack(config) {
+  config.resolve.alias = {
+    ...config.resolve.alias,
+    // your aliases
+  }
+}
+```
+
+### Useful Links
+
+- [Related issue](https://github.com/zeit/next.js/issues/6681)