I think Lukas Bach solution to use react-app-rewired in order to modify webpack config is a good way to go, however, I wouldn't exclude the whole ModuleScopePlugin but instead whitelist the specific file that can be imported outside of src:
config-overrides.js
const ModuleScopePlugin = require("react-dev-utils/ModuleScopePlugin");
const path = require("path");
module.exports = function override(config) {
config.resolve.plugins.forEach(plugin => {
if (plugin instanceof ModuleScopePlugin) {
plugin.allowedFiles.add(path.resolve("./config.json"));
}
});
return config;
};