fix(fslib): export CustomDir (#5371)

* Whitespace.

* Export CustomDir class.

To allow compatible implementations of `opendir` to be created by
consumers of this library.

.yarn/versions/fefcfcf9.yml

@@ -0,0 +1,36 @@
+releases:
+  "@yarnpkg/fslib": patch
+
+declined:
+  - "@yarnpkg/plugin-compat"
+  - "@yarnpkg/plugin-constraints"
+  - "@yarnpkg/plugin-dlx"
+  - "@yarnpkg/plugin-essentials"
+  - "@yarnpkg/plugin-exec"
+  - "@yarnpkg/plugin-file"
+  - "@yarnpkg/plugin-git"
+  - "@yarnpkg/plugin-github"
+  - "@yarnpkg/plugin-init"
+  - "@yarnpkg/plugin-link"
+  - "@yarnpkg/plugin-nm"
+  - "@yarnpkg/plugin-npm"
+  - "@yarnpkg/plugin-npm-cli"
+  - "@yarnpkg/plugin-pack"
+  - "@yarnpkg/plugin-patch"
+  - "@yarnpkg/plugin-pnp"
+  - "@yarnpkg/plugin-pnpm"
+  - "@yarnpkg/plugin-stage"
+  - "@yarnpkg/plugin-typescript"
+  - "@yarnpkg/plugin-version"
+  - "@yarnpkg/plugin-workspace-tools"
+  - vscode-zipfs
+  - "@yarnpkg/builder"
+  - "@yarnpkg/cli"
+  - "@yarnpkg/core"
+  - "@yarnpkg/doctor"
+  - "@yarnpkg/libzip"
+  - "@yarnpkg/nm"
+  - "@yarnpkg/pnp"
+  - "@yarnpkg/pnpify"
+  - "@yarnpkg/sdks"
+  - "@yarnpkg/shell"

packages/yarnpkg-fslib/sources/index.ts

@@ -6,9 +6,9 @@ export {constants};
 export {errors};
 export {statUtils};
 
-export type {LinkStrategy} from './algorithms/copyPromise';
-export {setupCopyIndex}    from './algorithms/copyPromise';
-export {opendir}           from './algorithms/opendir';
+export type {LinkStrategy}                       from './algorithms/copyPromise';
+export {setupCopyIndex}                          from './algorithms/copyPromise';
+export {opendir, CustomDir}                      from './algorithms/opendir';
 export {watchFile, unwatchFile, unwatchAllFiles} from './algorithms/watchFile';
 
 export {normalizeLineEndings}          from './FakeFS';