add sequelize typescript example

[agodin3z]

This PR adds an example of how to create a Restful API with Sequelize.

In the example, the "users" service includes a minimal CRUD to handle data with the various Sequelize methods.

[encore-cla[bot]]

All committers have signed the CLA.

[simon-johansson]

Thanks for the PR @agodin3z and sorry for the late reply! Looks great I fixed the conflict in the README.