Explain filters a bit more

README

@@ -51,6 +51,16 @@ that does not match those regexes.
 The default program is less(1).  For text files, you can use the 'v'
 commaind in less(1) to open the file in your $EDITOR.
 
+Filters
+-------
+
+Filters narrow down the view.  This effectively allows you to easily search/jump
+to a particular file or directory.  If you want to reset the filter then you can
+just use the match-any regex (i.e. .*).  You can think of noice being in search
+mode all the time.
+
+Filters do not stack or nest.  They are applied afresh every time.
+
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