Some `azuracast.env` variables missing

[mdrxy]

This section of the docs is missing a few vars that exist in the file that's in production:

• AUTO_ASSIGN_PORT_MAX
• SHOW_DETAILED_ERRORS
• NOW_PLAYING_DELAY_TIME
• NOW_PLAYING_MAX_CONCURRENT_PROCESSES
• PROFILING_EXTENSION_ALWAYS_ON
• PROFILING_EXTENSION_HTTP_KEY
• NGINX_CLIENT_MAX_BODY_SIZE
• ENABLE_WEB_UPDATER
• INSTALL_PACKAGES_ON_STARTUP

Honorable mention for LANG, though hopefully its self explanatory? Though given that things like MYSQL_USER are included in the docs, perhaps it is important to include everything for consistency?

Happy to PR this but would need to know what the consensus is for adding some of these.

[BusterNeece]

@mdrxy Feel free to PR this in. We just forget to update these docs from time to time. I'd say in most cases it's safe to use the definition text that's in our own PHP code (if it exists).