fix: handle `/editor` path for nginx

I changed package manager npm to yarn because I've got an error when building the image with docker.

TypeError [ERR_INVALID_ARG_TYPE]: The "path" argument must be of type string. Received type undefined

So It's fixed when I use yarn . There is no installation step for yarn because the node:14-buster image already contains it.

I'm new to Nginx. Maybe it can be solved in a better way

Fixes #67