Fix: Iterate over several pages to get all discussions

[jakubbortlik]

This is a naive fix for #182. I've just added a loop that goes over several pages of discussions to get more items than the default 100 allowed by Gitlab. gitlab.nvim tries to get 250, but cannot get more than 100 in one request.

[jakubbortlik]

Hi, @harrisoncramer, I'd like to ask for help in fixing the tests for this. I don't know how to do that, this is the first time I've read and written some go code :) I've had a look at the output of the test, but cannot make anything out of it.

After some trial and error I've made the tests pass, but I'm not sure the test are now the way you want them.

[jakubbortlik]

Closing, as the simple suggested solution conflicts with the newly added code for emojis and there'll certainly be a better way to fix the problem with unlisted discussions.