Execute and advance shortcut

[NduatiK]

Jupyter and Deepnote let us execute the current cell and advance to the next cell using Shift + Enter.
Could this also be supported in Livebook?

When reading through the documentation, sometimes you just want to run the current cell, see the result and move on to the next step.

Currently, you can hit Ctrl + Enter then k (a vim thing?) but I find the single button more comfortable given the convention in other notebooks.

[josevalim]

I have created issue #1277. A pull request is also welcome!

[NduatiK]

Thanks Jose, the change looks manageable, I will work on it this week.

[NduatiK]

Merged #1294