The type of sliding box animation could be changed from its init function

[MrGreensWorkshop]

About pull request

• To get more insight, please check the related issue #136 .

What's changed to accomplish [problem / feature] described in issue

• slide type class is removed from _includes/default/sliding-msg-box.html.
• language offer box has its own slide type setting.
• cookie consent setting box has its own slide type setting.
• slide type is passed to assets/js/_js/default/sliding-msg-box.js using init function.
• Now we can individually set the slide type for both the language offer box and the cookie consent setting box at _data/conf/main.yml.

Coding rule check is done [yes]