xdg-settings: add page (#8215)

pages/linux/xdg-settings.md

@@ -0,0 +1,24 @@
+# xdg-settings
+
+> Manage settings of XDG-compatible desktop environments.
+> More information: <https://portland.freedesktop.org/doc/xdg-settings.html>.
+
+- Print the default web browser:
+
+`xdg-settings get {{default-web-browser}}`
+
+- Set the default web browser to Firefox:
+
+`xdg-settings set {{default-web-browser}} {{firefox.desktop}}`
+
+- Set the default mail URL scheme handler to Evolution:
+
+`xdg-settings set {{default-url-scheme-handler}} {{mailto}} {{evolution.desktop}}`
+
+- Set the default PDF document viewer:
+
+`xdg-settings set {{pdf-viewer.desktop}}`
+
+- Display help:
+
+`xdg-settings --help`