Add MKRGSM1400 Websocket example, issue #46

[fechidal89]

Add an Echo WebSocket Client using MKRGSM1400.

[CLAassistant]

Thank you for your submission! We really appreciate it. Like many open source projects, we ask that you sign our Contributor License Agreement before we can accept your contribution.
_{You have signed the CLA already but the status is still pending? Let us recheck it.}