Add EmbedPaginator to menu module

[Andre601]

Pull Request

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Pull Request Information

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• [ ] My PR fixes a bug, error, or other issue with the library's codebase.
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Description

Closes #103

This implements a EmbedPaginator class to the menu module, which allows to pass own instances of a MessageEmbed to make paginated Embeds.

This is mostly based on the Slideshow class.

There are methods that where not implemented for multiple reasons:

• setColor and showPageNumber: Seems weird and would probably be a quite "hacky" aproach to alter an Embed's colour if you provide it through the MessageEmbed instance itself.
• setItemsPerPage: You can only have one embed per page, for obvious reasons.

I also added a addItems(String... items) and setItems(String... items) method to just create a basic Embed with nothing more than the description. That is just a convenience method in case someone wants this.

[Andre601]

I pushed some minor corrections to the overall format. In addition did I also add a Checks.check(String#length() <= MessageEmbed.TEXT_MAX_LENGTH, "Message"); check for the addItems(String...) and setItems(String...) methods to make sure that none of the provided Strings exceeds the embed limit.

[Andre601]

Added a addItems(Collection<MessageEmbed>) and setItems(Collection<MessageEmbed>) option.