chore: ignore .DS_Store file

[hideokamoto]

Description

In mac env, once open our project dir, the .DS_Store file will be create automatically. We don't want to commit the file, so we need to ignore the file.

Motivation and Context

When we want to contribute the project, the .DS_Store file disturb our workflow.

$ git status
On branch 2.0.x
Your branch is up-to-date with 'origin/2.0.x'.

Untracked files:
  (use "git add <file>..." to include in what will be committed)

        .DS_Store
        ask-sdk-core/.DS_Store
        ask-sdk-dynamodb-persistence-adapter/.DS_Store
        ask-sdk-runtime/.DS_Store
        ask-sdk-s3-persistence-adapter/.DS_Store
        ask-sdk-v1adapter/.DS_Store
        ask-sdk/.DS_Store

nothing added to commit but untracked files present (use "git add" to track)

We have to delete these file before run git add.

Testing

$ touch .DS_Store
$ git status

-> If the .DS_Store file does not show in the Untracked files list, it is OK.

Screenshots (if appropriate)

Types of changes

• [ ] Bug fix (non-breaking change which fixes an issue)
• [ ] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to change)
• [ ] Docs(Add new document content)
• [ ] Translate Docs(Translate document content)
• [x] Other

Checklist

• [ ] My code follows the code style of this project
• [ ] My change requires a change to the documentation
• [ x ] I have updated the documentation accordingly
• [ x ] I have read the README document
• [ x ] I have added tests to cover my changes
• [ x ] All new and existing tests passed
• [ x ] My commit message follows Conventional Commit Guideline

License

• [ x ] I confirm that this pull request can be released under the Apache 2 license