feat(dev): Make neovim available in gitpod

Part-of: <https://dev.funkwhale.audio/funkwhale/funkwhale/-/merge_requests/2734>

.gitpod/Dockerfile

@@ -6,6 +6,8 @@ RUN sudo apt update -y \
 
 RUN pyenv install 3.11 && pyenv global 3.11
 
+RUN brew install neovim
+
 RUN pip install poetry pre-commit jinja2 towncrier \
     && poetry config virtualenvs.create true \
     && poetry config virtualenvs.in-project true