Document code style

Author: Jaeho Yoo

development/process.md

@@ -18,6 +18,15 @@ The Trino project succeeds with your help and contributions. Find details on how
 to contribute, how maintainers assist, and more related information in the
 following sections:
 
+## Code style
+
+All contributions must follow the project's code style guidelines to ensure
+consistency and readability. For Java code, follow the [Trino Java code style guide](https://github.com/trinodb/trino/blob/master/DEVELOPMENT.md#code-style).
+For SQL and documentation, refer to the respective sections in the [development guide](https://github.com/trinodb/trino/blob/master/DEVELOPMENT.md).
+
+Before submitting a pull request, please format your code and check for style issues.  
+Consistent code style helps reviewers and maintainers focus on the logic and quality of your contribution.
+
 ## Contribution process
 
 This is the process we suggest for contributions.  This process is designed to
@@ -248,7 +257,7 @@ The following aspects apply for reviewing pull requests.
   understand and assess the security implications of running the test suite on
   the external service and ensure that no malicious code is run.
 
-### Pull request review and  merge
+### Pull request review and merge
 
 The following criteria and aspects apply for merging pull requests.