update misc/vim/README

misc/vim/README

@@ -13,15 +13,46 @@ The current set of files is as follows:
 	Teach Vim when to load Factor support files.
     ftplugin/factor_settings.vim
 	Teach Vim to follow the Factor Coding Style guidelines.
+    plugin/factor.vim
+	Teach Vim some commands for navigating Factor source code. See below.
     syntax/factor.vim
         Syntax highlighting for Factor code.
 
+The "plugin/factor.vim" file implements the following commands for
+navigating Factor source:
+
+    :FactorVocab factor.vocab.name
+        Opens the source file implementing the "factor.vocab.name"
+        vocabulary.
+    :FactorVocabImpl
+        Opens the main implementation file for the current vocabulary
+        (name.factor).  The keyboard shortcut "\fi" is bound to this
+        command.
+    :FactorVocabDocs
+        Opens the documentation file for the current vocabulary
+        (name-docs.factor).  The keyboard shortcut "\fd" is bound to this
+        command.
+    :FactorVocabTests
+        Opens the unit test file for the current vocabulary
+        (name-tests.factor).  The keyboard shortcut "\ft" is bound to this
+        command.
+
+In order for the ":FactorVocab" command to work, you'll need to set some
+variables in your vimrc file:
+    g:FactorRoot
+        This variable should be set to the root of your Factor
+        installation. The default value is "~/factor".
+    g:FactorVocabRoots
+        This variable should be set to a list of Factor vocabulary roots.
+        The paths may be either relative to g:FactorRoot or absolute paths.
+        The default value is ["core", "basis", "extra", "work"].
+
 Note: The syntax-highlighting file is automatically generated to include the
 names of all the vocabularies Factor knows about. To regenerate it manually,
 run the following code in the listener:
 
     "editors.vim.generate-syntax" run
 
-...or run it from the command-line:
+...or run it from the command line:
 
     factor -run=editors.vim.generate-syntax