Add kittygram as an Instagram frontend

[rootful]

kittygram is a frontend for Instagram, similar to Proxigram and now discontinued Bibliogram

Repo: https://codeberg.org/irelephant/kittygram

[antermin]

There is no new commit for Proxigram for nearly 2 years (last commit was 2024/02/29).
Their Wiki page of public instances lists 5 instances, but none of them is accessible now.

I hope maintainers can consider using kittygram to replace Proxigram. kittygram seems to be active and has 2 working instances (but due to Instagram's heavy rate-limiting, it is still possible that sometimes the frontend can't display posts).

[ManeraKai]

https://codeberg.org/LibRedirect/browser_extension/pulls/231