docs: list available filters for du and prune commands

Signed-off-by: CrazyMax <1951866+crazy-max@users.noreply.github.com>

docs/reference/buildx_du.md

@@ -13,7 +13,7 @@ Disk usage
 |:------------------------|:---------|:--------|:-----------------------------------------|
 | [`--builder`](#builder) | `string` |         | Override the configured builder instance |
 | `-D`, `--debug`         | `bool`   |         | Enable debug logging                     |
-| `--filter`              | `filter` |         | Provide filter values                    |
+| [`--filter`](#filter)   | `filter` |         | Provide filter values                    |
 | [`--format`](#format)   | `string` |         | Format the output                        |
 | [`--verbose`](#verbose) | `bool`   |         | Shorthand for `--format=pretty`          |
 
@@ -62,6 +62,10 @@ The asterisks (\*) in the default output format indicate the following:
   If you prune such a record then you will lose build cache but only metadata
   will be deleted as the image still needs to actual storage layers.
 
+### <a name="filter"></a> Provide filter values (--filter)
+
+Same as [`buildx prune --filter`](buildx_prune.md#filter).
+
 ### <a name="format"></a> Format the output (--format)
 
 The formatting options (`--format`) pretty-prints usage information output