Changed deploy to node server

Afaik, Nanostores need SSR in the setup I used, so for now, the build will have to be deployed on a node server.
I could have used a full Vue app to avoid this, but oh well, nothing we can't refactor ; and it just works anyways. Plus it would have meant switching to a vue leaflet wrapper that hasn't been maintained in years.
Can always change it later.

astro.config.mjs

@@ -1,8 +1,13 @@
 import { defineConfig } from 'astro/config';
+import nodeJs from '@astrojs/node';
 
 import vue from "@astrojs/vue";
 
 // https://astro.build/config
 export default defineConfig({
-  integrations: [vue()]
+    integrations: [vue()],
+    output: 'server',
+    adapter: nodeJs({
+        mode: 'standalone'
+    }),
 });