Reader for string unicode symbol values

There's a reader for symbol values that are stored as unicode
codepoints, but some types, particularly monsters, use a string to store
their symbol value. Add a reader that supports this, by converting the
codepoint from the codepoint reader to a string.

Author: ehughsbaird

src/generic_factory.cpp

@@ -78,6 +78,18 @@ bool unicode_codepoint_from_symbol_reader( const JsonObject &jo,
     return true;
 }
 
+bool unicode_symbol_reader( const JsonObject &jo, const std::string_view member_name,
+                            std::string &member, bool was_loaded )
+{
+    uint32_t codepoint;
+    bool read = unicode_codepoint_from_symbol_reader( jo, member_name, codepoint, was_loaded );
+    if( read ) {
+        member = utf32_to_utf8( codepoint );
+        return true;
+    }
+    return false;
+}
+
 float read_proportional_entry( const JsonObject &jo, std::string_view key )
 {
     if( jo.has_float( key ) ) {

src/generic_factory.h

@@ -960,6 +960,12 @@ bool one_char_symbol_reader( const JsonObject &jo, std::string_view member_name,
 bool unicode_codepoint_from_symbol_reader(
     const JsonObject &jo, std::string_view member_name, uint32_t &member, bool );
 
+/**
+ * unicode_codepoint_from_symbol_reader, but with a string instead of a codepoint
+ */
+bool unicode_symbol_reader( const JsonObject &jo, std::string_view member_name, std::string &member,
+                            bool was_loaded );
+
 //Reads a standard single-float "proportional" entry
 float read_proportional_entry( const JsonObject &jo, std::string_view key );