chore: Add VS Code devcontainer

.devcontainer/Dockerfile

@@ -0,0 +1,15 @@
+ARG VARIANT="buster"
+FROM mcr.microsoft.com/vscode/devcontainers/rust:0-${VARIANT}
+
+RUN apt-get update && export DEBIAN_FRONTEND=noninteractive
+RUN apt-get install libgtk-3-dev libssl-dev -y
+
+# generate completions
+RUN su vscode -c 'mkdir ~/.zfunc'
+RUN su vscode -c 'rustup completions zsh > ~/.zfunc/_rustup'
+RUN su vscode -c 'rustup completions zsh cargo > ~/.zfunc/_cargo'
+
+# load completions via .zshrc
+RUN su vscode -c 'echo fpath+=~/.zfunc >> ~/.zshrc'
+RUN su vscode -c 'echo autoload -U compinit >> ~/.zshrc'
+RUN su vscode -c 'echo compinit -i >> ~/.zshrc'