Document the filtering support of DirectoryTree

docs/examples/widgets/directory_tree_filtered.py

@@ -0,0 +1,20 @@
+from pathlib import Path
+from typing import Iterable
+
+from textual.app import App, ComposeResult
+from textual.widgets import DirectoryTree
+
+
+class FilteredDirectoryTree(DirectoryTree):
+    def filter_paths(self, paths: Iterable[Path]) -> Iterable[Path]:
+        return [path for path in paths if not path.name.startswith(".")]
+
+
+class DirectoryTreeApp(App):
+    def compose(self) -> ComposeResult:
+        yield FilteredDirectoryTree("./")
+
+
+if __name__ == "__main__":
+    app = DirectoryTreeApp()
+    app.run()