The ESLint config for the extension explicitly includes support for
Prettier. However, this is already being provided by our global ESLint
config (`@metamask/eslint-config`). Therefore there is no need to
include it here. In fact, this is causing weird issues where the `curly`
option is getting overridden somehow. After this change, these syntaxes
are invalid:
``` javascript
if (foo) return;
```
``` javascript
if (foo) return 'bar';
```
A propType error was showing up during e2e tests with a `testDev`
build. It was caused by `process.env.IN_TEST` being treated as a
boolean, when in fact it is either the string `'true'` or a boolean.
`IN_TEST` has been updated to always be a boolean. `loose-envify` has
no trouble injecting boolean values, so there's no reason to treat this
as a string.
