Update base container, clean up image

.dockerignore

@@ -30,3 +30,10 @@ yarn-debug.log*
 cardconjurer.iml
 access.log
 error.log
+
+# MF Additions
+launcher*
+.gitignore
+/.gitea
+Makefile
+README.md

Dockerfile

@@ -1,7 +1,7 @@
-# syntax = docker/dockerfile:1.2
-FROM nginx:1.21-alpine as prod
+FROM nginx:mainline-alpine
 
-EXPOSE 4242
 COPY . /usr/share/nginx/html/
 COPY app.conf /etc/nginx/nginx.conf
 
+EXPOSE 4242
+VOLUME [ "/usr/share/nginx/html/local_art" ]