docs(developer-guide): fix documented output dir path for grunt build artifacts (#1541)
docs(developer-guide): fix documented output dir path for grunt build artifacts (#1541)

`grunt build` produces axe.js and axe.min.js in the root folder. `dist` folder is not created.
dequelabs/axe-core,dequelabs/axe-core,dequelabs/axe-core,dequelabs/axe-core