Cell toolbar

[brichet]

Example to add cell toolbar buttons.

The buttons are displayed or not, depending on the cell type.

Fix #227

[jtpio]

Thanks @brichet, this looks good!

[jtpio]

Looks like there are a couple of conflicts.

Also should the new example be listed in the top-level README.md? https:/jupyterlab/extension-examples#develop-by-examples

[brichet]

Thanks @jtpio for looking this.

I rebased and fixed conflicts, and add la ink and a preview in README.

I also fixed 2 broken previews in README.

[brichet]

Tests are failing because jupyterlab/jupyterlab#14838 is not merged yet.

Probably #244 should have wait for it.

[jtpio]

Probably #244 should have wait for it.

Right, I don't know why the failure was ignored in that PR.

[jtpio]

Thanks!

[fcollonval]

Probably #244 should have wait for it.

Right, I don't know why the failure was ignored in that PR.

It is a chicken egg issue - the lab doc reference the example that reference the lab doc.

[fcollonval]

Feel free to finish up the doc pr on lab.