Add first dart solution

[NikSWE]

• File(s) Modified: 0217-contains-duplicate.dart
• Language(s) Used: dart
• Submission URL: https://leetcode.com/problems/contains-duplicate/submissions/870072859/

[NikSWE]

Hey @neetcode-gh

I want to add Dart solutions to the repo. I have made the required change in the workflow to update the table in the README.md file and added the first solution using Dart. Let me know if any further changes are required to get the Dart solutions up on the Neetcode.io website.

[NikSWE]

I was wondering how is the language dropdown build on Neetcode.io, is it static or dynamic?

[NikSWE]

Did a quick rebase to make it easier to merge the changes.

[NikSWE]

• File(s) Modified: 0242-valid-anagram.dart
• Language(s) Used: dart
• Submission URL: https://leetcode.com/problems/valid-anagram/submissions/870824844/

[NikSWE]

• File(s) Modified: 0036-valid-sudoku.dart
• Language(s) Used: dart
• Submission URL: https://leetcode.com/problems/valid-sudoku/submissions/870874554/

[NikSWE]

• File(s) Modified: 0001-two-sum.dart
• Language(s) Used: dart
• Submission URL: https://leetcode.com/problems/two-sum/submissions/870885709/

[NikSWE]

• File(s) Modified: 0049-group-anagrams.dart
• Language(s) Used: dart
• Submission URL: https://leetcode.com/problems/group-anagrams/submissions/870907518/

[neetcode-gh]

Thanks! For updating the site dropdown, I will prob get to that this weekend when I update the site data.