Update README.md

[abdemirza]

Added yarn install command in readme

Please provide enough information so that others can review your pull request:

Explain the details for making this change. What existing problem does the pull request solve?

Test plan (required)

Demonstrate the code is solid. Example: The exact commands you ran and their output, screenshots / videos if the pull request changes UI.

Code formatting

Closing issues

Put closes #XXXX in your comment and commit message to auto-close the issue that your PR fixes (if such).