fix(build): disable externalLiveBindings in rollup

`export * from '@testing-library/dom'` was causing issues where commonjs
imports would cause an error:

TypeError: Cannot set property fireEvent of #<Object> which has only a getter

Due to Rollbar adding a non-configurable property on `exports`

Setting `externalLiveBindings: false` uses simple assignment instead of
`Object.defineProperty`

rollup.config.js

@@ -10,7 +10,12 @@ const pkgDependencies = Object.keys({
 export default {
   input: 'src/index',
   output: [
-    {file: pkg.main, format: 'cjs', sourcemap: true},
+    {
+      file: pkg.main,
+      format: 'cjs',
+      sourcemap: true,
+      externalLiveBindings: false,
+    },
     {file: pkg.module, format: 'es', sourcemap: true},
   ],
   external: [...pkgDependencies],