Compiler config format from docs does not work

While [the docs say](https://relay.dev/docs/getting-started/installation-and-setup/#compiler-configuration) to make a `relay.config.js` file which exports an object, doing so doesn't actually work, as the compiler expects the file to be JSON, even if it is named `relay.config.js`.

Basic reproduction here: https://glitch.com/edit/#!/statuesque-jeweled-condorraptor

Here's what happens when you try to use different config files:

`relay.config.actually-json.js` is in JSON format, despite being named `.js`.

Read the compiler configuration section in the installation and setup docs, then reproduce the issue using the linked Glitch example and the named relay.config.js variants. Compare the documented JavaScript-object format with the compiler's accepted format; done means the documented configuration works or the docs accurately describe the required format.

Written by the indexing model from the issue text.