Recognise commonly sourced files as shellscript (#121373)

Added files commonly sourced by display managers.

- `.xsession` and its variants referenced in `/etc/X11/Xsession`
- `.xprofile` referenced in `/etc/gdm3/Xsession`

This PR fixes #121372.

extensions/shellscript/package.json

@@ -35,6 +35,10 @@
           ".install",
           ".profile",
           ".bash_logout",
+          ".xprofile",
+          ".xsession",
+          ".xsessionrc",
+          ".Xsession",
           ".zsh",
           ".zshrc",
           ".zprofile",