Run librephotos from URL subdirectory

If librephotos is installed along other apps on same server or running behind reverse proxy it will be good to be able to run it from a subdirectory. Now it is running always from / and will be good to have option to run from /librephotos, for example.

I tried to use librephotos docker images behind apache ssl terminating reverse proxy as https://example.com/librephotos, but api calls and almost any other urls are broken even if I use ProxyHTMLURLMap in apache.