If it's not a problem, then I would say it's rude for potential users and bad practice for developers.

The README transfers almost 100mb. If I'm on my phone with no wifi and I see an interesting repo as I'm a neovim user, I will just lose 100mb from my data plan with no warning. One doesn't expect that when visiting the README of a code repository.

Then what happens when they change something that makes the gifs obsolete? Will they add a commit with updated gifs that doubles the size of the repository? Most developers use

  git clone $URL

which copies the entire repo history, instead of using `--depth 1`. So now if someone wants to contribute a small change, they have to download hundreds of MBs of gifs.