Allow to save/load code in local storage #115
Description
Let's save/load the code from the browser's local storage. That might work smoothly even without github login, etc.
It would not require internet access and one could save work and close the browser. This is related to #20, which makes the browser freeze.
Some information about local storage: https://developer.mozilla.org/en-US/docs/Learn/JavaScript/Client-side_web_APIs/Client-side_storage