fix(babel): add support for commonjs requires.

Also includes codecov integration.

BREAKING CHANGE: Existing imports will have to change from
```
const conditionalImporter = require('node-sass-conditional-importer').default;
```
to
```
const conditionalImporter = require('node-sass-conditional-importer');
```

Author: codebymikey

.babelrc

@@ -0,0 +1,8 @@
+module.exports = {
+  presets: [
+    [
+      '@babel/preset-env',
+    ],
+  ],
+  plugins: ['add-module-exports'],
+}

.babelrc.js

@@ -6,6 +6,7 @@ their (environment) extension prefix, similar to React Native's
 
 [![npm](https://img.shields.io/npm/v/node-sass-conditional-importer.svg)](https://www.npmjs.com/package/node-sass-conditional-importer)
 [![build status](https://travis-ci.org/codebymikey/node-sass-conditional-importer.svg?branch=master)](https://travis-ci.org/codebymikey/node-sass-conditional-importer)
+[![Codecov Coverage](https://img.shields.io/codecov/c/github/codebymikey/node-sass-conditional-importer/coverage.svg?style=flat-square)](https://codecov.io/gh/codebymikey/node-sass-conditional-importer/)
 
 It reads in a list of `environments` extension prefixes, which it'll attempt to use over the default file.
 

README.md

@@ -1,6 +1,6 @@
 {
   "name": "node-sass-conditional-importer",
-  "version": "0.0.0-development",
+  "version": "0.0.0-semantically-released",
   "description": "A node-sass importer for dynamically/conditionally resolving files based on their file extension prefix.",
   "repository": {
     "type": "git",
@@ -51,6 +51,8 @@
     "@semantic-release/changelog": "^5.0.1",
     "@semantic-release/git": "^9.0.0",
     "babel-eslint": "^10.1.0",
+    "babel-plugin-add-module-exports": "^1.0.4",
+    "codecov": "^3.8.1",
     "commitizen": "^4.2.2",
     "cz-conventional-changelog": "^3.3.0",
     "eslint": "^7.11.0",

package-lock.json

@@ -4,6 +4,8 @@ import sass from 'node-sass';
 import path from 'path';
 
 import conditionalImporter from '../src';
+// Test both commonjs and ES6 import compatibility.
+const conditionalImporterCommonJS = require('../src');
 
 describe('conditionalImporter', () => {
   test('resolves the development _style.scss partial', function () {
@@ -127,7 +129,7 @@ describe('conditionalImporter', () => {
         file: './test/fixtures/partials/main.scss',
         outputStyle: 'compressed',
         importer: [
-          conditionalImporter({
+          conditionalImporterCommonJS({
             // Pass in a string.
             environments: 'production',
           }),