docs: Fix link to docs/logging.md

Previous link `docs/logging` is not valid, replacing `docs/logging` with
`docs/logging.md`.

Format `logging.md` using `mdformat` with GitHub Flavored Markdown
(GFM).

Signed-off-by: Ruoqing He <heruoqing@iscas.ac.cn>

docs/logging.md

@@ -2,8 +2,8 @@
 
 The target audience of this document is both:
 
-* Developers who want to understand what log level to use and when,
-* Users who want to debug issues with running their workloads in Cloud Hypervisor
+- Developers who want to understand what log level to use and when,
+- Users who want to debug issues with running their workloads in Cloud Hypervisor
 
 ## Control
 
@@ -29,7 +29,6 @@ A typical example of where this level of message should be generated is during a
 
 The user should investigate the meaning of this warning and take steps to ensure the correct functionality.
 
-
 ### `info!()`
 
 Use `-v` to enable.
@@ -40,4 +39,4 @@ This level is for the benefit of developers. It should be used for sporadic and
 
 Use `-vv` to enable.
 
-For the most verbose of logging messages. It is acceptable to "spam" the log with repeated invocations of the same message. This level of logging would be combined with `--log-file`.
+For the most verbose of logging messages. It is acceptable to "spam" the log with repeated invocations of the same message. This level of logging would be combined with `--log-file`.

release-notes.md

@@ -2533,7 +2533,7 @@ resources.
 
 The default logging level was changed to include warnings which should make it
 easier to see potential issues. New [logging
-documentation](docs/logging) was also added.
+documentation](docs/logging.md) was also added.
 
 ### New `--balloon` Parameter Added