Add a nginx config file which includes the required cors headers

Dockerfile

@@ -12,5 +12,6 @@ RUN yarn build
 
 FROM nginxinc/nginx-unprivileged:1.21.6
 
+COPY ./default-nginx.conf /etc/nginx/conf.d/default.conf
 COPY --from=build /app/target/assets /usr/share/nginx/html/assets
 COPY --from=build /app/target/chatterbox.html /usr/share/nginx/html/chatterbox.html

default-nginx.conf

+server {
+    listen       8080;
+    server_name  localhost;
+
+
+    location / {
+        if ($request_method = 'OPTIONS') {
+            add_header 'Access-Control-Allow-Origin' '*';
+            add_header 'Access-Control-Allow-Methods' 'GET';
+            #
+            # Custom headers and headers various browsers *should* be OK with but aren't
+            #
+            add_header 'Access-Control-Allow-Headers' 'DNT,User-Agent,X-Requested-With,If-Modified-Since,Cache-Control,Content-Type,Range';
+            #
+            # Tell client that this pre-flight info is valid for 20 days
+            #
+            add_header 'Access-Control-Max-Age' 1728000;
+            add_header 'Content-Type' 'text/plain; charset=utf-8';
+            add_header 'Content-Length' 0;
+            return 204;
+        }
+        if ($request_method = 'GET') {
+            add_header 'Access-Control-Allow-Origin' '*' always;
+            add_header 'Access-Control-Allow-Methods' 'GET' always;
+            add_header 'Access-Control-Allow-Headers' 'DNT,User-Agent,X-Requested-With,If-Modified-Since,Cache-Control,Content-Type,Range' always;
+            add_header 'Access-Control-Expose-Headers' 'Content-Length,Content-Range' always;
+        }
+        root   /usr/share/nginx/html;
+        index  chatterbox.html;
+    }
+
+    error_page   500 502 503 504  /50x.html;
+    location = /50x.html {
+        root   /usr/share/nginx/html;
+    }
+}
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