quick frontend (app): added "explicit_close" to deleteWidget, and use it on mucRoomLeftHandler: This flag can be used by frontends to decide if the widget must be really closed or not (otherwise, it may be interesting to keep a widget in memory to avoir recreating a new one each time that the chat must be displayed).

You'll find install instructions in documentation (see doc/installation.rst).

If you need help, come the SàT official XMPP room: sat@chat.jabberfr.org or join us with a web browser via https://chat.jabberfr.org/converse.js/sat@chat.jabberfr.org