Add pagination to /online and vocation filtering

[Galarzaa90]

To keep consistency between commands, /online should have pagination, like /findteam

Compared to online:

This would also avoid having issues when there's too many characters online and the limit is exceeded. Probably a long shot since the limit is 2048, but it would make answers on normal channels shorter, to encourage people to use the ask channel.

Another planned feature is vocation filters with reactions. Clicking on a reaction to filter that vocation ( 🔥 🏹 ❄️ 🛡 )

Vocation filtering would be added to /findteam and to the command described in #39 too.

[Galarzaa90]

Progress: https://gyazo.com/e21e1458112f09c03426fdc1bb54cac1

[Galarzaa90]

Known bugs:

• After filtering, the number of pages is not updated, i.e. the results had 3 pages, but after filtering druids, they only fill 2 pages. You can still go to the third page, but it will be empty Fixed in 1b6835abcedd82b4417f7a8eefc6298897e24867
• If there's not enough entries to require pages, filters are not shown. I might leave it that way.

Todo:

• Fix bugs, obviously
• Right now, to disable a filter, you have to react to that same filter again, so if you filtered druids, you react ❄️ again to show all. I want to change this so your reactions for filters are not automatically removed, instead, if you react ❄️, and then react 🔥, you will now see both druids and sorcerers. If you remove your ❄️ reaction, you will see only sorcerers, and if you remove your 🔥 reaction, you will see all vocations again. Right now you can only filter one vocation at once.

[Galarzaa90]

This will be left as it is for now.