Add paging and count limits

[voxpelli]

Eventually someone will get very many mentions and it will be unfeasible to show them all at once. Paging should be introduced both in the embeds and in the curlable views introduced in #18.

In the embeds the count should be configurable. On the standalone page it should probably have a fixed, high default – like eg. 100 – which would probably be the highest maximum to allow anywhere.

[voxpelli]

Have it work with a caching mechanism as well, as noted here: https://twitter.com/sil/status/1514950630066036743