spectacle: add page (#9552)

pages/common/spectacle.md

@@ -0,0 +1,16 @@
+# spectacle
+
+> KDE's screenshot utility.
+> More information: <https://manned.org/spectacle>.
+
+- Capture a screenshot of the entire desktop:
+
+`spectacle`
+
+- Capture a screenshot of the active window:
+
+`spectacle --activewindow`
+
+- Capture a screenshot of a specific region:
+
+`spectacle --region`