Make the specification of max-buffer-size discoverable. (#20562)

* Make the specification of max-buffer-size discoverable.

It's not obvious what type of strings are accepted by `max-buffer-size` nor is it obvious what e.g. `4m` means. Four _minutes_? (to me, it looks like something accepted by [ParseDuration](https://pkg.go.dev/time#ParseDuration).

Instead we should direct users to the relevant documentation to explain clearly what's allowed and what the units are.

* Update configure.md

Author: antonysouthworth-halter

content/engine/logging/configure.md

@@ -150,9 +150,11 @@ STDERR or STDOUT streams block.
 The `mode` log option controls whether to use the `blocking` (default) or
 `non-blocking` message delivery.
 
-The `max-buffer-size` log option controls the size of the buffer used for
-intermediate message storage when `mode` is set to `non-blocking`. `max-buffer-size`
-defaults to 1 megabyte.
+The `max-buffer-size` controls the size of the buffer used for
+intermediate message storage when `mode` is set to `non-blocking`.
+The default is `1m` meaning 1 MB (1 million bytes).
+See [function `FromHumanSize()` in the `go-units` package](https://pkg.go.dev/github.com/docker/go-units#FromHumanSize) for the allowed format strings,
+some examples are `1KiB` for 1024 bytes, `2g` for 2 billion bytes.
 
 The following example starts an Alpine container with log output in non-blocking
 mode and a 4 megabyte buffer: