Allow to do custom actions

[GCorbel]

No description provided.

[eduardoweiland]

Good work! 😄

Can you please split the custom action example from the index in the dummy app? Create a new route for "Custom actions". The Home example should be simpler and easy to understand, without too many customizations.

[eduardoweiland]

Add the option hideable: false so that this column does not appear on the column chooser menu, or add a label. Also, change this in the example snippet.

[GCorbel]

Done!

[eduardoweiland]

Please, revert the changes to tests/dummy/snippets/simple-table.js. The code for the tabs and collapse is used on the dummy app, but is not needed in the example snippets.
Also, use a component in the Custom Actions Example, as is already used in the other examples.

[GCorbel]

You're right. I did it. I found a little bit painful to maintain the snippets. Maybe there is a way to make it simpler. I know this is not really hard but, because it doesn't fail if there is something wrong, we have to be very careful.