Flag images are sourced from here:
https://flaglog.com/country-codes
Placing the flags in a subdirectory of `./static` for good housekeeping
requires a change to the location matching of the `nginx` configuration;
otherwise they will not be found.
Change:
```
location ~ /(?![^/]*\.(?:css|js|png|html)(?:$|\?)) {
```
to:
```
location ~ /(?!([^/]*|flags/[^/]*)\.(?:css|js|png|html)(?:$|\?)) {
```
