Fix flow parens in maybe types

Author: amadeus

extras/flow.vim

@@ -22,7 +22,7 @@ syntax region  jsFlowReturnArray    contained matchgroup=jsFlowNoise start=/\[/
 syntax region  jsFlowReturnParens   contained matchgroup=jsFlowNoise start=/(/    end=/)/  contains=@jsFlowCluster skipwhite skipempty nextgroup=jsFuncBlock,jsFlowReturnOrOp,jsFlowReturnArrow fold
 syntax match   jsFlowReturnArrow    contained /=>/ skipwhite skipempty nextgroup=@jsFlowReturnCluster
 syntax match   jsFlowReturnKeyword  contained /\k\+/ contains=jsFlowType,jsFlowTypeCustom skipwhite skipempty nextgroup=jsFlowReturnGroup,jsFuncBlock,jsFlowReturnOrOp,jsFlowReturnArray
-syntax match   jsFlowReturnMaybe    contained /?/ skipwhite skipempty nextgroup=jsFlowReturnKeyword,jsFlowReturnObject
+syntax match   jsFlowReturnMaybe    contained /?/ skipwhite skipempty nextgroup=jsFlowReturnKeyword,jsFlowReturnObject,jsFlowReturnParens
 syntax region  jsFlowReturnGroup    contained matchgroup=jsFlowNoise start=/</ end=/>/ contains=@jsFlowCluster skipwhite skipempty nextgroup=jsFuncBlock,jsFlowReturnOrOp
 syntax match   jsFlowReturnOrOp     contained /\s*|\s*/ skipwhite skipempty nextgroup=@jsFlowReturnCluster
 syntax match   jsFlowWildcardReturn contained /*/ skipwhite skipempty nextgroup=jsFuncBlock