Update README.md with Open in Codeanywhere button

[marko-baric-ca]

This PR adds "Open in Codeanywhere" badge at the top of Readme file.

Codeanywhere is a cloud-based Integrated Development Environment (IDE) that allows developers to code, learn, build, and collaborate on projects directly from their web browsers. This button opens the Codeanywhere VS Code IDE in the browser, pulls the repo, sets up a container environment and allows the developer to run the code - all of this with a single click and for free.

This removes the local setup hassle and allows developers to start coding and run the app in minutes, straight from the repo page in Github.

[tongbaochen]

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[li-phone]

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