Exposed escapeForJSON() in kiwix namespace

Note that it is declared in stringTools.h but its definition remains in
otherTools.cpp (to minimize the diff).

src/tools/otherTools.cpp

@@ -327,10 +327,7 @@ std::string kiwix::render_template(const std::string& template_str, kainjow::mus
   return ss.str();
 }
 
-namespace
-{
-
-std::string escapeForJSON(const std::string& s)
+std::string kiwix::escapeForJSON(const std::string& s)
 {
   std::ostringstream oss;
   for (char c : s) {
@@ -345,6 +342,9 @@ std::string escapeForJSON(const std::string& s)
   return oss.str();
 }
 
+namespace
+{
+
 std::string makeFulltextSearchSuggestion(const std::string& lang,
                                          const std::string& queryString)
 {

src/tools/stringTools.h

@@ -53,6 +53,7 @@ private:
   const icu::Locale locale;
 };
 
+std::string escapeForJSON(const std::string& s);
 
 /* urlEncode() is the equivalent of JS encodeURIComponent(), with the only
  * difference that the slash (/) symbol is NOT encoded. */