add nginx config for react-router

Dockerfile

@@ -10,5 +10,6 @@ RUN npm run build
 # production environment
 FROM nginx:1.16.0-alpine
 COPY --from=build /usr/src/app/build /usr/share/nginx/html
+COPY default.conf /etc/nginx/conf.d/default.conf
 EXPOSE 80
 CMD ["nginx", "-g", "daemon off;"]

default.conf

+server {
+    listen       80;
+    server_name  localhost;
+    location / {
+        try_files $uri /index.html;
+        root   /usr/share/nginx/html;
+        index  index.html index.htm;
+    }
+    error_page   500 502 503 504  /50x.html;
+}
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