enable rootless image (#1202)

Author: tomassatka

Dockerfile

@@ -1,5 +1,6 @@
 FROM nginx:1.21-alpine
 COPY dist/hypertrace-ui /usr/share/nginx/html
 COPY conf/default.conf /etc/nginx/conf.d/default.conf
+RUN chmod a+w /var/cache/nginx /var/run
 EXPOSE 2020
 HEALTHCHECK --interval=1s --retries=5 --timeout=1s CMD wget -qO- http://localhost:2020/graphql?query={__schema{queryType{name}}} &> /dev/null || exit 1