docs: add stubs for all commands

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

docs/reference/buildx_imagetools.md

@@ -0,0 +1,19 @@
+# buildx imagetools
+
+```
+Usage:  docker buildx imagetools [OPTIONS] COMMAND
+
+Commands to work on images in registry
+
+Options:
+      --builder string   Override the configured builder instance
+
+Commands:
+  create      Create a new image based on source images
+  inspect     Show details of image in the registry
+```
+
+## Description
+
+Imagetools contains commands for working with manifest lists in the registry.
+These commands are useful for inspecting multi-platform build results.