kreadconfig5: add page (#5293)

pages/linux/kreadconfig5.md

@@ -0,0 +1,16 @@
+# kreadconfig5
+
+> Read KConfig entries for KDE Plasma.
+> More information: <https://userbase.kde.org/KDE_System_Administration/Configuration_Files>.
+
+- Read a key from the global configuration:
+
+`kreadconfig5 --group {{group_name}} --key {{key_name}}`
+
+- Read a key from a specific configuration file:
+
+`kwriteconfig5 --file {{path/to/file}} --group {{group_name}} --key {{key_name}}`
+
+- Check if systemd is used to start the Plasma session:
+
+`kreadconfig5 --file {{startkderc}} --group {{General}} --key {{systemdBoot}}`