Merge pull request #597 from searxng/docker-upgrade-baseimage

Dockerfile: use alpine 3.15

Dockerfile

@@ -1,4 +1,4 @@
-FROM alpine:3.14
+FROM alpine:3.15
 ENTRYPOINT ["/sbin/tini","--","/usr/local/searxng/dockerfiles/docker-entrypoint.sh"]
 EXPOSE 8080
 VOLUME /etc/searx