add label dev.containers.timestamp

devops/Dockerfile

@@ -60,5 +60,9 @@ RUN chsh -s /usr/bin/zsh vscode
 RUN git clone https://github.com/zdharma-continuum/fast-syntax-highlighting.git /home/vscode/.oh-my-zsh/custom/plugins/fast-syntax-highlighting
 RUN git clone https://github.com/zsh-users/zsh-autosuggestions /home/vscode/.oh-my-zsh/custom/plugins/zsh-autosuggestions
 
+# --- copy assets ---
 COPY ./assets/.zshrc /home/vscode
 
+# --- labels ---
+LABEL dev.containers.timestamp="$(date -u +'%Y-%m-%dT%H:%M:%SZ')"
+