fix a fuzzing issue from a string as a bracket (#1110)

fix fuzzing issue

---------

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

book/chapters/config.md

@@ -259,6 +259,26 @@ The config parser has a modifier
 This modification will insert the separator between each line even if not
 sequential. This allows an input option to be configured with multiple lines.
 
+```toml
+# Examples of vector of vector inputs in config
+
+# this example is how config_to_str writes it out
+vector1 = [a,v,"[]"]
+```
+
+The field insertion has a special processing for duplicate characters starting
+with "[[" in which case the `"[]"` gets translated to `[[]]` before getting
+passed into the option which converts it back into the correct string. This can
+also be used on the command line to handle unusual parsing situation with
+brackets.
+
+### Argument With Brackets
+
+There is an edge case with actual strings that are surrounded by brackets. For
+example if the string "[]" needed to be passed. this would normally trigger the
+bracket processing and result in an empty vector. In this case it can be
+enclosed in quotes and should be handled correctly.
+
 ## Multiple configuration files
 
 If it is desired that multiple configuration be allowed. Use