message: Fix 'superfluous config key found' warnings with default config
  The previous implementation of `softLoadFont` added nodes to _usedKeys
  incorrectly, so the got warnings when starting the app with the default
  config.
diff: @@ -934,22 +934,24 @@ void softLoadFont(UsedKeys& _usedKeys,
  }
  else if (node.IsMap())
  {
  + _usedKeys.emplace(fmt::format("{}.{}", _basePath, _key));
  +
  if (node["family"].IsScalar())
  {
  - _usedKeys.emplace(fmt::format("{}.{}", _basePath, "family"));
  + _usedKeys.emplace(fmt::format("{}.{}.{}", _basePath, _key, "family"));
  _store.familyName = node["family"].as<string>();
  }
  if (node["slant"].IsScalar())
  {
  - _usedKeys.emplace(fmt::format("{}.{}", _basePath, "slant"));
  + _usedKeys.emplace(fmt::format("{}.{}.{}", _basePath, _key, "slant"));
  if (auto const p = text::make_font_slant(node["slant"].as<string>()))
  _store.slant = p.value();
  }
  if (node["weight"].IsScalar())
  {
  - _usedKeys.emplace(fmt::format("{}.{}", _basePath, "weight"));
  + _usedKeys.emplace(fmt::format("{}.{}.{}", _basePath, _key, "weight"));
  if (auto const p = text::make_font_weight(node["weight"].as<string>()))
  _store.weight = p.value();
  }
  