Bring back babel (#3974)

* Bring back babel

* bump preset env

* Remove empty TS properties in mixins

build-scripts/babel.js

@@ -3,7 +3,7 @@ module.exports.babelLoaderConfig = ({ latestBuild }) => {
     throw Error("latestBuild not defined for babel loader config");
   }
   return {
-    test: /\.m?js$/,
+    test: /\.m?js$|\.tsx?$/,
     use: {
       loader: "babel-loader",
       options: {
@@ -12,6 +12,12 @@ module.exports.babelLoaderConfig = ({ latestBuild }) => {
             require("@babel/preset-env").default,
             { modules: false },
           ],
+          [
+            require("@babel/preset-typescript").default,
+            {
+              jsxPragma: "h",
+            },
+          ],
         ].filter(Boolean),
         plugins: [
           // Part of ES2018. Converts {...a, b: 2} to Object.assign({}, a, {b: 2})
@@ -21,6 +27,12 @@ module.exports.babelLoaderConfig = ({ latestBuild }) => {
           ],
           // Only support the syntax, Webpack will handle it.
           "@babel/syntax-dynamic-import",
+          [
+            "@babel/transform-react-jsx",
+            {
+              pragma: "h",
+            },
+          ],
           [
             require("@babel/plugin-proposal-decorators").default,
             { decoratorsBeforeExport: true },