DOCS: add clipboard documentations

DOCS/interface-changes/clipboard.txt

@@ -0,0 +1,2 @@
+add `--clipboard-enable` and `--clipboard-monitor` options
+add `clipboard` property

DOCS/man/input.rst

@@ -3894,6 +3894,23 @@ Property list
 
     This property is read-only, and change notification is not supported.
 
+``clipboard``
+    The clipboard contents, only works when native clipboard
+    (``--clipboard-enable``) is supported on the platform.
+    Depending on the platform, some sub-properties, writing to properties,
+    or change notifications are not currently functional.
+
+    This has a number of sub-properties:
+
+    ``clipboard/text`` (RW)
+        The text content in the clipboard (Windows and Wayland only).
+        Writing to this property sets the text clipboard content (Windows only).
+
+    .. note::
+
+        On Wayland, the clipboard content is only updated when the compositor
+        sends a selection data offer (typically when VO window is focused).
+
 Inconsistencies between options and properties
 ----------------------------------------------
 

DOCS/man/options.rst

@@ -7814,3 +7814,18 @@ Miscellaneous
     code is the same.)
 
     Conversion is not applied to metadata that is updated at runtime.
+
+``--clipboard-enable=<yes|no>``
+    (Windows and Wayland only)
+
+    Enable native clipboard support (default: yes). This allows reading and
+    writing to the ``clipboard`` property to get and set clipboard contents.
+
+``--clipboard-monitor=<yes|no>``
+    (Windows only)
+
+    Enable clipboard monitoring so that the ``clipboard`` property can be
+    observed for content changes (default: no). This only affects clipboard
+    implementations which use polling to monitor clipboard updates.
+    Other platforms currently ignore this option and always/never notify
+    changes.