fix error: change `./config` to `./config.js`
fix error: change `./config` to `./config.js`

Error when using ./config in development. It d/n appear when using `data-env="production"`

GET http://localhost:63342/stealjs-progressive-loading/site/config 404 (Not Found)
steal.js:5334 steal - error loading @config. Not Found: http://localhost:63342/stealjs-progressive-loading/site/config

stealjs/steal-tools,mcanthony/steal-tools,stealjs/steal-tools,mcanthony/steal-tools