Docx writer: set paragraph to FirstPara after display math

We treat display math like block quotes, and apply FirstParagraph style
to paragraphs that follow them. These can be styled as the user
wishes. (But, when the user is using indentation, this allows for
paragraphs to continue after display math without indentation.)

src/Text/Pandoc/Writers/Docx.hs

@@ -1045,6 +1045,7 @@ inlineToOpenXML opts (Math mathType str) = do
   let displayType = if mathType == DisplayMath
                        then DisplayBlock
                        else DisplayInline
+  when (displayType == DisplayBlock) setFirstPara
   case writeOMML displayType <$> readTeX str of
         Right r -> return [r]
         Left  _ -> inlinesToOpenXML opts (texMathToInlines mathType str)