Allow devDependencies for foo_spec.js naming style

Some projects name test files like `foo_spec.js` instead of `foo.spec.js`.

Author: lencioni

packages/eslint-config-airbnb-base/rules/imports.js

@@ -76,7 +76,7 @@ module.exports = {
         '**/__tests__/**', // jest pattern
         'test.{js,jsx}', // repos with a single test file
         'test-*.{js,jsx}', // repos with multiple top-level test files
-        '**/*.{test,spec}.{js,jsx}', // tests where the extension denotes that it is a test
+        '**/*{.,_}{test,spec}.{js,jsx}', // tests where the extension or filename suffix denotes that it is a test
         '**/jest.config.js', // jest config
         '**/webpack.config.js', // webpack config
         '**/webpack.config.*.js', // webpack config