added the possibility to manage animations

[biou]

It might be interesting to add an option in AccessConfig to manage animations. This has been done in the accessibility parameters of other websites, for example sncf.fr.

Compared to other AccessConfig parameters, animations can often be managed by JavaScript, so we should find a way to notify this code of some changes in the settings. There are several ways to do this, I propose to use a callback function, mainly because it is simple to use and does not need a polyfill like custom events in old versions of IE.

What do you think, is it interesting?

[DuaelFr]

This MR looks good to me. It's working as expected and I like that there is a callback for JS to react to the change.
Thanks! I hope this could be merged officially!

[biou]

This MR looks good to me. It's working as expected and I like that there is a callback for JS to react to the change.
Thanks! I hope this could be merged officially!

Thanks for your support!
I discussed this PR with @access42 a long time ago and I think that this approach has some limits, but I don't remember what it was. Maybe it is just too complex for front-end developers. To be double-checked with them. If you need this feature, feel free to fork this repo and integrate this PR. All feedback is of course welcome!