Add support to directly add MessageEmbeds to Paginator

[Andre601]

Issue

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Description

The paginator, while nice to use, is limited in how much you can customize it.
In fact, other than changing, if the page number should be shown in the footer, the color and the actual description itself is the Paginator not that customizable, considering it using embeds.

My suggestion is to implement support, to directly provide MessageEmbed(s) through a addItems(MessageEmbed...) method.

Why do I not implement it?
The current code of the Paginator is way too strict and complicated, as that it would allow to directly add MessageEmbeds without an entire recode (Unless you guys know a proper way).
I wanted to implement it myself, but it's just way too much and would result on an entire recode on my end, which is not what I want to achieve here, as this would also be a difficult part in a PR.

[jagrosh]

This sounds like it should be a new menu type

[Andre601]

I mean sure, but why exactly? I can see many people to want this functionality in the Paginator itself to f.e. show more detailed command-lists with like thumbnails or custom colours...

[jagrosh]

The primary purpose of the paginator is to split up the items into the appropriate-sized lists automatically, provide page numbers, etc.... supplying your own embeds prevents it from doing any of this. If you're supplying your own embeds, there's no paginator functionality anymore, just the general menu functionality of press-reaction->change-view.

[jagrosh]

Providing a custom embed is actually much closer functionality to the Slideshow than to the Paginator

[Andre601]

Considering this, did I now try my best to create a EmbedPaginator class for achieving this goal.
I made a PR on my fork so that you guys can take a look.

[Andre601]

I made some basic testing with it and it seems to work without errors or issues.