Apply suggestions from code review

Co-authored-by: Sutou Kouhei <[email protected]>

_posts/2023-10-03-nanoarrow-0.3.0-release.md

@@ -34,7 +34,7 @@ See the
 [Changelog](https://github.com/apache/arrow-nanoarrow/blob/apache-arrow-nanoarrow-0.3.0/CHANGELOG.md)
 for a detailed list of contributions to this release.
 
-## C library
+### C library
 
 The nanoarrow 0.3.0 release includes a number of bugfixes and improvements
 to the core C library and IPC C extension:
@@ -47,7 +47,7 @@ to the core C library and IPC C extension:
 - Fixed crashes that occurred for certain types of corrupted data and improved
   error messages that were misleading for other types of corrupted data.
 
-## R bindings
+### R bindings
 
 The nanoarrow R bindings are distributed as the `nanoarrow` package on
 [CRAN](https://cran.r-project.org/). The 0.3.0 release of the R bindings includes
@@ -62,7 +62,7 @@ improvements in type support and stability. Notably:
 - Improved performance of stream conversion to R vectors for streams of
   indeterminate length (e.g., database results from ADBC).
 
-## Experimental non-CPU support
+### Experimental non-CPU support
 
 With the addition of the
 [Arrow C Device data interface](https://arrow.apache.org/docs/format/CDeviceDataInterface.html)
@@ -72,18 +72,18 @@ extension was drafted in tandem with the specification and Arrow C++ implementat
 While it is not an official part of the 0.3.0 release, it is available in an
 experimental state for those interested in its use and/or development.
 
-## Contributor experience
+### Contributor experience
 
 The 0.3.0 release features adoption of `pre-commit` hooks to improve consistency
 and contributor experience with a complex repository. Special thanks to
 [@WillAyd](https://github.com/WillAyd) for setting this up!
 
 ## Contributors
 
-This initial release consists of contributions from 4 contributors in addition
+This release consists of contributions from 4 contributors in addition
 to the invaluable advice and support of the Apache Arrow developer mailing list.
 
-```
+```console
 $ git shortlog -sn d4f038ce58655ba6e996cdae165f1b33c3919d51..apache-arrow-nanoarrow-0.3.0 | grep -v "GitHub Actions"
     40  Dewey Dunnington
      7  William Ayd