doc update

doc/implementation.tex

@@ -25,6 +25,7 @@ Your Javascript program is stored into the Program Memory, and since its capacit
 \1\inlinesynopsis[Array]{init}{}{returns the subarray that omits the \emph{last} element.}
 \1\inlinesynopsis[Array]{sum}{selector}{returns the sum of the elements of the array. Selector is optionally defined to indicate how the value must be transformed to obtain the sum.}
 \1\inlinesynopsis[Array]{max}{selector}{returns the maximum among the elements of the array. Selector is optionally defined to indicate how the value must be transformed to obtain the max.}
+\1\inlinesynopsis[String]{trimNull}{}{trims null characters at the \emph{end} of the string.}
 \end{outline}