Test yard and update contributing

Author: Yang-33

.github/workflows/pull_request.yml

@@ -35,6 +35,7 @@ jobs:
     - run: bundle install
     - run: bundle exec rubocop
     - run: bundle exec rspec
+    - run: bundle exec yard stats ./lib/line/bot/v2 --fail-on-warning
 
   rbs:
     runs-on: ubuntu-latest

CONTRIBUTING.md

@@ -1,15 +1,45 @@
-## How to contribute to LINE Bot SDK for Ruby project
+# How to contribute to LINE Bot SDK for Ruby project
 
-First of all, thank you so much for taking your time to contribute! LINE Bot SDK for Ruby is not very different from any other open
-source projects you are aware of. It will be amazing if you could help us by doing any of the following:
+First of all, thank you so much for taking your time to contribute!
+LINE Bot SDK for Ruby is not very different from any other open source projects you are aware of.
+It will be amazing if you could help us by doing any of the following:
 
-- File an issue in [the issue tracker](https://github.com/line/line-bot-sdk-ruby/issues) to report bugs and propose new features and
-  improvements.
+- File an issue in [the issue tracker](https://github.com/line/line-bot-sdk-ruby/issues) to report bugs and propose new features and improvements.
 - Ask a question using [the issue tracker](https://github.com/line/line-bot-sdk-ruby/issues).
 - Contribute your work by sending [a pull request](https://github.com/line/line-bot-sdk-ruby/pulls).
 
+## Development
+
+### YARD
+
+We use [YARD](https://yardoc.org) to generate and maintain our code documentation.
+**Please make sure your new or modified code is also covered by proper YARD doc comments.**
+Good documentation ensures that contributors and users can easily read and understand how the methods and classes work.
+
+#### How to generate and view documentation locally
+
+##### 1. **Start a local documentation server**
+
+Run the following command to start a local YARD server that will automatically reload when files change:
+
+```bash
+bundle exec yard server --reload
+```
+
+Then open the printed URL in your browser (e.g., http://localhost:8808).
+
+##### 2. **Validate your documentation**  
+
+Before pushing your changes, run the following command to check YARD documentation coverage and warnings:
+```bash
+bundle exec yard stats ./lib/line/bot/v2 --fail-on-warning
+```
+This will fail if there are missing doc comments or any YARD-specific warnings.
+Make sure to fix any issues before creating a pull request.
+
+For more details on how to write YARD doc comments, refer to YARD’s official [Getting Started guide](https://rubydoc.info/gems/yard/file/docs/GettingStarted.md).
+
 ### Contributor license agreement
 
-When you are sending a pull request and it's a non-trivial change beyond fixing typos, please make sure to sign
-[the ICLA (individual contributor license agreement)](https://cla-assistant.io/line/line-bot-sdk-ruby). Please
-[contact us](mailto:dl_oss_dev@linecorp.com) if you need the CCLA (corporate contributor license agreement).
+When you are sending a pull request and it's a non-trivial change beyond fixing typos, please make sure to sign [the ICLA (individual contributor license agreement)](https://cla-assistant.io/line/line-bot-sdk-ruby).
+Please [contact us](mailto:dl_oss_dev@linecorp.com) if you need the CCLA (corporate contributor license agreement).

Gemfile

@@ -6,7 +6,9 @@ gem 'multipart-post', '~> 2.4.1', require: false
 
 group :development, :test do
   # ref: http://docs.rubocop.org/en/latest/installation/
+  gem 'rack', '~> 2.2'
   gem 'rubocop', '~> 1.75.0', require: false
+  gem 'webrick', '~> 1.9.1'
   gem 'yard', '~> 0.9.20'
 end
 

Gemfile.lock

@@ -27,6 +27,7 @@ GEM
     prism (1.4.0)
     public_suffix (6.0.1)
     racc (1.8.1)
+    rack (2.2.13)
     rainbow (3.1.1)
     rake (13.2.1)
     regexp_parser (2.10.0)
@@ -66,20 +67,24 @@ GEM
       addressable (>= 2.8.0)
       crack (>= 0.3.2)
       hashdiff (>= 0.4.0, < 2.0.0)
+    webrick (1.9.1)
     yard (0.9.37)
 
 PLATFORMS
+  arm64-darwin-21
   arm64-darwin-22
   x86_64-linux
 
 DEPENDENCIES
   addressable (~> 2.3)
   line-bot-api!
   multipart-post (~> 2.4.1)
+  rack (~> 2.2)
   rake (~> 13.0)
   rspec (~> 3.13.0)
   rubocop (~> 1.75.0)
   webmock (~> 3.25.0)
+  webrick (~> 1.9.1)
   yard (~> 0.9.20)
 
 BUNDLED WITH