Added Encode and Decode TinyURL in Csharp

[mriitian]

• File(s) Modified: 0535-encode-and-decode-tinyurl.cs, 0838-push-dominoes.js
• Language(s) Used: csharp, javascript
• Submission URL: https://leetcode.com/problems/encode-and-decode-tinyurl/submissions/1215281005/ , https://leetcode.com/problems/push-dominoes/submissions/1216244764/

Important

Please make sure the file name is lowercase and a duplicate file does not already exist before merging.