chore: Add CONTRIBUTING.md (#30)

## What's Changed

* Use [Conventional
Commits](https://www.conventionalcommits.org/en/v1.0.0/)
* But use only `fix` (for patch release) , `feat` (for minor release)
and `chore` (other changes) for easy to maintain
* Need a GitHub issue for any change except "minor changes"

Closes #11.

Author: kou

CONTRIBUTING.md

@@ -0,0 +1,122 @@
+<!---
+  Licensed to the Apache Software Foundation (ASF) under one
+  or more contributor license agreements.  See the NOTICE file
+  distributed with this work for additional information
+  regarding copyright ownership.  The ASF licenses this file
+  to you under the Apache License, Version 2.0 (the
+  "License"); you may not use this file except in compliance
+  with the License.  You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+  Unless required by applicable law or agreed to in writing,
+  software distributed under the License is distributed on an
+  "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+  KIND, either express or implied.  See the License for the
+  specific language governing permissions and limitations
+  under the License.
+-->
+
+# How to contribute to Apache Arrow Swift
+
+We utilize [Conventional
+Commits](https://www.conventionalcommits.org/en/v1.0.0/) for our
+commit messages. This helps maintain the semantic versioning of this
+module.
+
+Please use the following commit types: `chore`, `feat`, `fix`.
+
+If a PR includes any breaking change, please add `!` such as `feat!`
+and `fix!`.
+
+We will use these commit types to determine the next version. If we
+have only `fix` (and `chore`) changes, we will increase the patch
+version. If we have any `feat` change, we will increase the minor
+version. If we have any `feat!` or `fix!` change, we will increase the
+major version.
+
+For example:
+
+```
+fix: Handle empty structs in C data interface
+
+fix!: Fix performance regression with API change
+
+chore: Update CI environment
+
+feat: Support new encoding type
+
+feat!: Reconstruct API
+```
+
+## Did you find a bug?
+
+The Arrow Swift project uses GitHub as a bug tracker. To report a bug,
+sign in to your GitHub account, navigate to [GitHub
+issues](https://github.com/apache/arrow-swift/issues) and click on
+**New issue** .
+
+Before you create a new bug entry, we recommend you first search among
+existing issues in
+[GitHub](https://github.com/apache/arrow-swift/issues).
+
+## Did you write a patch that fixes a bug or brings an improvement?
+
+- Create a GitHub issue and submit your changes as a GitHub Pull Request.
+- [Reference the issue](https://docs.github.com/en/issues/tracking-your-work-with-issues/using-issues/linking-a-pull-request-to-an-issue#linking-a-pull-request-to-an-issue-using-a-keyword) in your PR description.
+- Add the PR title. The PR title will be used as the eventual commit message, so please make it descriptive but succinct.
+
+Example #1:
+
+```
+chore: Document the pull request process
+
+## What's Changed
+
+Explain how to open a pull request and what the title, body, and labels should be.
+
+Closes #12345.
+```
+
+Example #2:
+
+```
+feat: Expose Netty server builder in Flight
+
+## What's Changed
+
+Allow direct usage of gRPC APIs for low-level control.
+
+Closes #42424.
+```
+
+### Minor fixes
+
+Any functionality change should have a GitHub issue opened. For minor
+changes that affect documentation, you do not need to open up a GitHub
+issue. If your changes meet one of the following, they're minor
+changes:
+
+*  Grammar, usage and spelling fixes that affect no more than 2 files
+*  Documentation updates affecting no more than 2 files and not more
+   than 500 words.
+
+## Do you want to propose a significant new feature or an important refactoring?
+
+We ask that all discussions about major changes in the codebase happen
+publicly on the GitHub issues or [arrow-dev
+mailing-list](https://lists.apache.org/[email protected]).
+
+## Do you have questions about the source code, the build procedure or the development process?
+
+You can also ask on the [arrow-dev
+mailing-list](https://lists.apache.org/[email protected])
+or [GitHub
+Discussions](https://github.com/apache/arrow-swift/discussions).
+
+## Further information
+
+Please read our [development
+documentation](https://arrow.apache.org/docs/developers/index.html) or
+look through the [New Contributor's
+Guide](https://arrow.apache.org/docs/developers/guide/index.html).