✨(frontend) introduce frontend Docker image

Inspired by the Docker images from numerique-gouv/people and numerique-gouv/impress
(see commit 1a3b396 in the "people" repository).

Due to the lack of a certified cold storage solution (e.g., S3) for serving static files,
we've containerized the frontend as a temporary deployment solution.

Vite.js static output is served using an Nginx reverse proxy.

I am not quite sure of this commit, please @manuhabitela could you review how I exposed
the static build from vite in my Nginx server? and do the appriopriate fix if necessary.

src/frontend/default.conf

@@ -0,0 +1,15 @@
+server {
+  listen 8080;
+  server_name localhost;
+
+  root /usr/share/nginx/html;
+
+  location / {
+      try_files $uri index.html $uri/ =404;
+  }
+
+  error_page 404 /404.html;
+  location = /404.html {
+      internal;
+  }
+}