bump docker base image to alpine 3.18

Fixes #2103

Dockerfile

 RUN make install
 
 ## build ergo container
-FROM docker.io/alpine:3.13
+FROM docker.io/alpine:3.18
 
 # metadata
 LABEL maintainer="Daniel Oaks <daniel@danieloaks.net>,Daniel Thamdrup <dallemon@protonmail.com>" \