Update src/literals.h

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

Author: mathieucarbou

src/literals.h

@@ -25,7 +25,7 @@
 namespace asyncsrv {
 
 static constexpr const char empty[] = "";
-static const String emptyString;
+inline const String emptyString{};
 
 static constexpr const char T__opaque[] = "\", opaque=\"";
 static constexpr const char T_100_CONTINUE[] = "100-continue";