not overwrite the interface_config.js

[ProgrammerMao]

This issues about two other issues: #886 and #275 , I want like in issues 275, don't to revise soures code, and revise the interface_config.js also working
I don't know it can or not work, just revise the file https://github.com/jitsi/docker-jitsi-meet/blob/master/web/rootfs/etc/cont-init.d/10-config ,if the target file already exist,could avoid overwriting

[damencho]

You can create a custom-interface_config.js and put your settings there which will take effect after booting the images.