Provide some alternative hints about the `tmp` folder

Currently within the env.example file is reported the following statement:

g3w-suite-docker/.env.example

Lines 4 to 6 in 0850ede

    
           # Shared volume mount (docker internal: shared-volume) 
        
           # I suggest not to use the /tmp/ folder, /tmp/ folder is cleaned at each reboot 
        
           WEBGIS_DOCKER_SHARED_VOLUME=/tmp/shared-volume-g3wsuite-dev

in addition to that it would also be better to indicate some examples of folders recommended or quite common for you (then everyone is free to use what they want, but at least we have a common starting point).

Have a nice day,
Raruto

	# Shared volume mount (docker internal: shared-volume)
	# I suggest not to use the /tmp/ folder, /tmp/ folder is cleaned at each reboot
	WEBGIS_DOCKER_SHARED_VOLUME=/tmp/shared-volume-g3wsuite-dev