Changing the link for Community Examples

[Abduttayyeb]

With the removal of examples/community directory, the link for Community examples under Most Important Links in README.md resulted in a 404 landing page hence correcting it by adding this link https://devlibrary.withgoogle.com/ as mentioned here https://github.com/tensorflow/examples/pull/304#issue-617101055

Instead, if this link needs to be removed too, will do that after the review by maintainers.