Add note that writable: true applies recursively.

Author: Peter Amstutz

v1.0/CommandLineTool.yml

@@ -759,6 +759,9 @@ $graph:
         the original file or directory.  Default false (files and directories
         read-only by default).
 
+        A directory marked as `writable: true` implies that all files and
+        subdirectories are recursively writable as well.
+
 
 - name: InitialWorkDirRequirement
   type: record

v1.1.0-dev1/CommandLineTool.yml

@@ -810,6 +810,8 @@ $graph:
         the original file or directory.  Default false (files and directories
         read-only by default).
 
+        A directory marked as `writable: true` implies that all files and
+        subdirectories are recursively writable as well.
 
 - name: InitialWorkDirRequirement
   type: record