feat: add typescript support for dev config (#262)

Adds a new `babel-typescript` preset.

config/babel-typescript.config.js

@@ -0,0 +1,5 @@
+const config = require('./babel.config');
+
+config.presets.push('@babel/preset-typescript');
+
+module.exports = config;

config/webpack.dev.config.js

@@ -37,19 +37,20 @@ module.exports = merge(commonConfig, {
   },
   resolve: {
     alias: aliases,
+    extensions: ['.js', '.jsx', '.ts', '.tsx'],
   },
   module: {
     // Specify file-by-file rules to Webpack. Some file-types need a particular kind of loader.
     rules: [
       // The babel-loader transforms newer ES2015+ syntax to older ES5 for older browsers.
       // Babel is configured with the .babelrc file at the root of the project.
       {
-        test: /\.(js|jsx)$/,
+        test: /\.(js|jsx|ts|tsx)$/,
         exclude: /node_modules\/(?!@edx)/,
         use: {
           loader: 'babel-loader',
           options: {
-            configFile: presets.babel.resolvedFilepath,
+            configFile: presets['babel-typescript'].resolvedFilepath,
             // Caches result of loader to the filesystem. Future builds will attempt to read
             // from the cache to avoid needing to run the expensive recompilation process
             // on each run.

lib/presets.js

@@ -14,6 +14,12 @@ const babelPreserveModules = new ConfigPreset({
   searchFilepaths,
 });
 
+const babelTypescript = new ConfigPreset({
+  defaultFilename: 'babel-typescript.config.js',
+  searchFilenames: ['babel-typescript.config.js', '.babelrc', '.babelrc.js', 'babel.config.js'],
+  searchFilepaths,
+});
+
 const eslint = new ConfigPreset({
   defaultFilename: '.eslintrc.js',
   searchFilenames: ['.eslintrc', '.eslintrc.js'],
@@ -48,6 +54,7 @@ module.exports = {
   babel,
   babelPreserveModules,
   'babel-preserve-modules': babelPreserveModules,
+  'babel-typescript': babelTypescript,
   eslint,
   jest,
   webpack,