Document the clipboard kitten

docs/kittens/clipboard.rst

@@ -0,0 +1,27 @@
+clipboard - copy/paste to the system clipboard
+==================================================
+
+.. highlight:: sh
+
+
+The ``clipboard`` kitten can be used to read or write to the system clipboard
+from the shell. It even works over SSH. Using it is as simple as::
+
+    echo hooray | kitty +kitten clipboard
+
+All text received on :file:`stdin` is copied to the clipboard.
+
+To get text from the clipboard you have to enable reading of the clipboard
+in :opt:`clipboard_control` in :file:`kitty.conf`. Once you do that, you can
+use::
+
+    kitty +kitten clipboard --get-clipboard
+
+
+.. program:: kitty +kitten clipboard
+
+
+Command Line Interface
+--------------------------
+
+.. include:: /generated/cli-kitten-clipboard.rst