Copy doc_src to sphinx_doc_src and add a TOC

sphinx_doc_src/cmds/not.rst

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+\section not not - negate the exit status of a job
+
+\subsection not-synopsis Synopsis
+\fish{synopsis}
+not COMMAND [OPTIONS...]
+\endfish
+
+\subsection not-description Description
+
+`not` negates the exit status of another command. If the exit status is zero, `not` returns 1. Otherwise, `not` returns 0.
+
+
+\subsection not-example Example
+
+The following code reports an error and exits if no file named spoon can be found.
+
+\fish
+if not test -f spoon
+    echo There is no spoon
+    exit 1
+end
+\endfish
+