Allow extra plugin for Ckeditor

[WedgeSama]

For now, the config.extraPlugin of Ckeditor is set during the initcke without taking the default value.
The PR just check if there is a value in config.extraPlugin and if it does, it will not be ignore.

This allow you to set the default global CKEDITOR.config.extraPlugin without loosing it. (for example to add table advanced plugin).

If necessary, I can PR for 3.0 too.

[bobdenotter]

Will this change mean you can add extra CKeditor plugins via config.yml? If so, could you update config.yml.dist to say so?

If necessary, I can PR for 3.0 too.

Yes please. Bolt 2.2 is in "bugfix only mode". This means we're not adding new features to Bolt 2.2.x anymore.

[SvanteRichter]

Also, perhaps some docs besides the config.yml.dist comment/key would be nice.

[GwendolenLynch]

@SahAssar assigning you as sponsor for this.

@WedgeSama as mentioned above, 2.2 is in bug fix mode, so we're going to re-target this against current master (which will land soon in 3.1).

Over to you, @SahAssar 😉

[SvanteRichter]

@WedgeSama If you could retarget this to master it would be awesome, after it is merged (and we have some docs for it) we/I can tinker with getting a hook for extensions to be able to add ckeditor plugins too :)

[GwendolenLynch]

Merged into master via c4a2efe