Update docs

docfx/api/Mono.Terminal/Mono.Terminal.MainLoop.Condition.yml

@@ -18,7 +18,7 @@ items:
   assemblies:
   - Terminal.Gui
   namespace: Mono.Terminal
-  summary: Condition on which to wake up from file descriptor activity
+  summary: Condition on which to wake up from file descriptor activity.  These match the Linux/BSD poll definitions.
   syntax:
     content: >-
       [System.Flags]

docfx/api/Mono.Terminal/Mono.Terminal.MainLoop.yml

@@ -27,6 +27,9 @@ items:
   summary: >-
     Simple main loop implementation that can be used to monitor
                   file descriptor, run timers and idle handlers.
+  remarks: >-
+    Monitoring of file descriptors is only available on Unix, there
+                  does not seem to be a way of supporting this on Windows.
   syntax:
     content: public class MainLoop
   inheritance: