runtime(sh) Update sh syntax and add shDblParen to shCaseList (#13469)

Signed-off-by: Christian Brabandt <cb@256bit.org>

Author: Lucien Grondin

runtime/syntax/sh.vim

@@ -140,7 +140,7 @@ syn cluster shArithList	contains=@shArithParenList,shParenError
 syn cluster shCaseEsacList	contains=shCaseStart,shCaseLabel,shCase,shCaseBar,shCaseIn,shComment,shDeref,shDerefSimple,shCaseCommandSub,shCaseExSingleQuote,shCaseSingleQuote,shCaseDoubleQuote,shCtrlSeq,@shErrorList,shStringSpecial,shCaseRange
 syn cluster shCaseList	contains=@shCommandSubList,shCaseEsac,shColon,shCommandSub,shCommandSubBQ,shComment,shDblBrace,shDo,shEcho,shExpr,shFor,shHereDoc,shIf,shHereString,shRedir,shSetList,shSource,shStatement,shVariable,shCtrlSeq
 if exists("b:is_kornshell") || exists("b:is_bash")
- syn cluster shCaseList	add=shForPP
+ syn cluster shCaseList	add=shForPP,shDblParen
 endif
 syn cluster shCommandSubList	contains=shAlias,shArithmetic,shCmdParenRegion,shCommandSub,shComment,shCtrlSeq,shDeref,shDerefSimple,shDoubleQuote,shEcho,shEscape,shExDoubleQuote,shExpr,shExSingleQuote,shHereDoc,shNumber,shOperator,shOption,shPosnParm,shHereString,shRedir,shSingleQuote,shSpecial,shStatement,shSubSh,shTest,shVariable
 syn cluster shCurlyList	contains=shNumber,shComma,shDeref,shDerefSimple,shDerefSpecial