Add labels to Docker images

Dockerfile

@@ -13,3 +13,8 @@ FROM nginx as ki-frontend
 
 COPY --from=builder /dist/ /usr/share/nginx/html/
 COPY etc/nginx/conf.d/default.conf /etc/nginx/conf.d/default.conf
+
+LABEL org.opencontainers.image.source=https://git.wtf-eg.de/kompetenzinventar/ki-frontend.git
+LABEL org.opencontainers.image.url=https://git.wtf-eg.de/kompetenzinventar/ki-frontend
+LABEL org.opencontainers.image.documentation=https://git.wtf-eg.de/kompetenzinventar/ki-frontend#docker
+LABEL org.opencontainers.image.vendor="WTF Kooperative eG"