add delimiters (#2)

Co-authored-by: Rob Farrow <rob@fibberist.com>

README.md

@@ -278,12 +278,21 @@ The purpose of this shorthand is to improve readability and standardize on eleme
 Line cannot start with a back-tic.  Body text requires an element.  Content back-tic is last feature on a line.
 A line that starts with plus '+' is a continuation of the attributes on the line above.  May be followed by a space.
 
+Using simple back string (or rawstring):
 ```brief
 elem:foo bar:zed
     + more:true range:"3 to 5" `
   more content here`
 ```
 
+Or using special hash delimiter (#| |#, #@ @#, #$ $#, #% %#) for when you need a nested rawstring ``
+```brief
+elem:foo bar:zed
+    + more:true range:"3 to 5" #|
+  more content here
+  |#
+```
+
 ### Include files
 
 To keep files modular the #include directive allows other brief files to be inserted.  The decoder handles indentation for you so each file can be indented naturally from zero.  Include directives insert files so they can be treated like any other sub-element.