nginx-proxy-manager/rootfs/etc/nginx/conf.d/include/assets.conf

location ~* ^.*\.(css|js|jpe?g|gif|png|woff|eot|ttf|svg|ico|css\.map|js\.map)$ {
    if_modified_since off;

    # use the public cache
    proxy_cache public-cache;
    proxy_cache_key $host$request_uri;

    # ignore these headers for media
    proxy_ignore_headers Set-Cookie Cache-Control Expires X-Accel-Expires;

    # cache 200s and also 404s (not ideal but there are a few 404 images for some reason)
    proxy_cache_valid any 30m;
    proxy_cache_valid 404 1m;

    # strip this header to avoid If-Modified-Since requests
    proxy_hide_header Last-Modified;
    proxy_hide_header Cache-Control;
    proxy_hide_header Vary;

    proxy_cache_bypass 0;
    proxy_no_cache 0;

    proxy_cache_use_stale error timeout updating http_500 http_502 http_503 http_504 http_404;
    proxy_connect_timeout 5s;
    proxy_read_timeout 45s;

    expires @30m;
    access_log  off;

    include conf.d/include/proxy.conf;
}