docs: standardize format for usage

Use the usage output of `--help` for each subcommand, to make
sure all flags/options are included on the page, and to make
it easier to keep docs in sync.

Note that the usage output is only used when reading these
docs on GitHub; docs.docker.com only consumes the "description"
and "example" sections (when present), and generates flag information
and usage output from source

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

docs/reference/buildx_stop.md

@@ -1,4 +1,13 @@
-# `buildx stop [NAME]`
+# buildx stop
+
+```
+Usage:  docker buildx stop [NAME]
+
+Stop builder instance
+
+Options:
+      --builder string   Override the configured builder instance
+```
 
 ## Description