WebKitGtk 6 enforces sandbox web process but for it to work properly one
has to configure the sandbox to have access to
XDG_RUNTIME_DIR (contains Wayland/X11 display sockets) and /tmp
(temporary files).

Fixes a crash when opening Welcome/Internal Web Browser views or Help
system with
```
(process:2): Gtk-WARNING **: 14:56:39.676: Failed to open display

** (Eclipse:1773443): ERROR **: 14:56:39.750: readPIDFromPeer:
Unexpected short read from PID socket. (This usually means the auxiliary
process crashed immediately. Investigate that instead!)
```