Input/output signals, zoneless, test suite added

[madebyjeffrey]

referencing #11

A test suite was added to validate certain behaviours were being executed on codemirror, then inputs were swapped.

All lifecycle methods removed
Zoneless used (updated code property in demo application everything else looked fine - this is the only thing that really requires to angular 20)

I cannot guarantee everything is covered despite my best efforts.

[nzbin]

Many thanks for your PR, I'm not ready for converting the lib to signals at the moment because of the component’s backward compatibility. In addition, the Angular Material still uses the decorator Input.

Do you have issues using the lib in a signal app? Maybe I will increase the support for signals. I can merge your PR to the signals branch at first.

[madebyjeffrey]

I am looking to get into the signal based forms and zoneless and this was a good first step.

I needed a code editor and this component was perfect and there was an issue already.