Fix Staging server 404 error (#22)

Dockerfile

@@ -1,2 +1,5 @@
 FROM nginx
 COPY ./out /usr/share/nginx/html
+
+COPY staging-nginx.conf /etc/nginx/conf.d
+RUN rm /etc/nginx/conf.d/default.conf

next.config.js

@@ -1,6 +1,7 @@
 /** @type {import('next').NextConfig} */
 const nextConfig = {
   reactStrictMode: true,
+  trailingSlash: true,
 }
 
 module.exports = nextConfig

staging-nginx.conf

@@ -0,0 +1,10 @@
+server {
+    listen 80;
+    location / {
+      root   /usr/share/nginx/html;
+      index  index.html index.htm;
+      try_files $uri $uri/ $uri.html $uri.html/ /index.html;
+    } 
+    error_page 404 /index.html;
+  }
+