swift: palindromic-number

[KaalidArare]

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## I Am Adding a New Code Snippet in an Existing Language

• I fixed Add Palindromic Number to Swift #4033
• I named the pull request using Add {palindromic-number} in {swift} format

I Am Adding a New Code Snippet in a New Language

• I fixed #your-issue-number-here
• I named the pull request using Add {PROJECT} in {LANGUAGE} format
• I added a testinfo.yml files (see contributing documentation)
  • I used an officially supported docker image or one that I personally trust

I Am Adding New Tests for a Project

• I fixed #your-issue-number-here
• I named the pull request using Add {PROJECT} Tests format
• I verified the project exists on the Sample Programs Project List
• I added tests for every test case in the Testing table of the project description for the given project. (See contributing documentation)

I Am Adding New Tests for a Language

• I fixed #your-issue-number-here
• I named the pull request using Add {LANGUAGE} Tests format
• I added a testinfo.yml files (see contributing documentation)
  • I used an officially supported docker image or one that I personally trust
• I verified all tests are passing

I Am Modifying an Existing Code Snippet or Existing Tests

• I fixed #your-issue-number-here
• I have read about modifying existing code snippets or tests in the contributing documentation
• I have explained why this modification is necessary either in the issue linked above or in the notes below
• I named the pull request using Modify {PROJECT} {tests} in {LANGUAGE} format

Other Notes

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[rzuckerm]

This is a duplicate of #4033