fix to use const eval on advise of @SolitudeSF

Author: gpicron

src/jsony.nim

@@ -736,11 +736,9 @@ proc dumpHook*(s: var string, v: string) =
       s.dumpStrFast(v)
 
 template dumpKey(s: var string, v: string) =
-  var escaped = newStringOfCap(v.len + 5)
-  dumpHook(escaped, v)
-  escaped.add ":"
-  s.add escaped
-  
+  const v2 = jsony.toJson(v) & ":"
+  s.add v2
+
 proc dumpHook*(s: var string, v: char) =
   s.add '"'
   s.add v