Make LuaStack::Load return special codes for 'slash command', 'white space', and 'truncated lua'

luprex/cpp/core/util.cpp

@@ -199,6 +199,15 @@ bool is_lua_comment(string_view s) {
     return s.substr(start, 2) == "--";
 }
 
+bool is_whitespace(string_view s) {
+    for (int i = 0; i < int(s.size()); i++) {
+        if (!ascii_isspace(s[i])) {
+            return false;
+        }
+    }
+    return true;
+}
+
 string_view read_to_sep(string_view &source, char sep) {
     size_t pos = source.find(sep);
     string_view result;