[meta.trans.other] Add index entry for invoke_result.

Author: Eelis

source/meta.tex

@@ -1896,6 +1896,7 @@
  otherwise, there is no member \tcode{type}.\br
  \mandates \tcode{T} is not an incomplete enumeration type. \\ \rowsep
 
+\indexlibraryglobal{invoke_result}%
 \tcode{template<class Fn,}\br
  \tcode{class... ArgTypes>}\br
  \tcode{struct invoke_result;}