Add documentation for TaskProgressColumn

docs/source/progress.rst

@@ -163,6 +163,7 @@ The following column objects are available:
 - :class:`~rich.progress.TransferSpeedColumn` Displays transfer speed (assumes the steps are bytes).
 - :class:`~rich.progress.SpinnerColumn` Displays a "spinner" animation.
 - :class:`~rich.progress.RenderableColumn` Displays an arbitrary Rich renderable in the column.
+- :class:`~rich.progress.TaskProgressColumn` Displays task completion progress as a percentage.
 
 To implement your own columns, extend the :class:`~rich.progress.ProgressColumn` class and use it as you would the other columns.
 
@@ -296,3 +297,20 @@ Example
 -------
 
 See `downloader.py <https://github.com/willmcgugan/rich/blob/master/examples/downloader.py>`_ for a realistic application of a progress display. This script can download multiple concurrent files with a progress bar, transfer speed and file size.
+
+TaskProgressColumn
+~~~~~~~~~~~~~~~~~~
+
+The ``TaskProgressColumn`` displays the percentage of task completion.
+
+It is typically used to show how much of a task has been completed relative to
+its total value. This column is included in the default progress columns and is
+useful when tracking long-running tasks.
+
+Example::
+
+    from rich.progress import Progress, TaskProgressColumn
+
+    progress = Progress(
+        TaskProgressColumn(),
+    )