Show dot when there is no visible cursor

Disabled by default.

docs/API.md

@@ -53,6 +53,11 @@ protocol stream.
     should be sent whenever the container changes dimensions. Disabled
     by default.
 
+`showDotCursor`
+  - Is a `boolean` indicating whether a dot cursor should be shown
+    instead of a zero-sized or fully-transparent cursor if the server
+    sets such invisible cursor. Disabled by default.
+
 `capabilities` *Read only*
   - Is an `Object` indicating which optional extensions are available
     on the server. Some methods may only be called if the corresponding

docs/EMBEDDING.md

@@ -61,6 +61,9 @@ query string. Currently the following options are available:
 * `resize` - How to resize the remote session if it is not the same size as
   the browser window. Can be one of `off`, `scale` and `remote`.
 
+* `show_dot` - If a dot cursor should be shown when the remote server provides
+  no local cursor, or provides a fully-transparent (invisible) cursor.
+
 * `logging` - The console log level. Can be one of `error`, `warn`, `info` or
   `debug`.