Add b&w Weblate logo

[milotype]

1. Add a black & white svg Weblate logo (linking to https://hosted.weblate.org/engage/kotatsu/) to the options in the top right corner of the website with Telegram, Discord and GitHub logos.

Screenshot 1

2. Add a black & white svg Weblate logo (linking to https://hosted.weblate.org/engage/kotatsu/) to the options in the footer with GitHub, Discord and Telegram logos.

Screenshot 2

You can download the black & white svg Weblate logo at https://www.iconarchive.com/show/simple-icons-by-simpleicons-team/weblate-icon.html.

Sorry, I couldn't find where to make the changes on GitHub :-(