Add CW keying, function key messages and the documentation

The function keys send through cwdaemon or a WinKeyer, with N1MM's message
macros. Escape stops sending.

Settings are read with the reflection serializer rather than a generated one:
the generated one hands back null for every property the file leaves out
instead of the value the property is declared with, which crashed the program
the first time a new setting was added.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

src/Nonemm.App/Windows/EntryWindow.axaml

@@ -51,6 +51,7 @@
         <MenuItem Header="_Radio…" Click="OnRadioSettings" />
         <MenuItem Header="_Cluster…" Click="OnClusterSettings" />
         <MenuItem Header="_Network…" Click="OnNetworkSettings" />
+        <MenuItem Header="_Keyer and messages…" Click="OnKeyerSettings" />
         <Separator />
         <MenuItem Header="Download Country _File" Click="OnDownloadCountryFile" />
         <MenuItem Header="Download Check _Partial File" Click="OnDownloadCallDatabase" />