(clean): remove --env=jsdom as JSDOM is Jest's default (#396)

- the React template and docs for it had --env=jsdom explicitly set,
  but there's no need to do this, as Jest uses JSDOM by default already

- setting it a second time in CLI also overrides any custom configs

README.md

@@ -449,7 +449,7 @@ Examples
 
 ### `tsdx test`
 
-This runs Jest v24.x in watch mode. See [https://jestjs.io](https://jestjs.io) for options. If you are using the React template, jest uses the flag `--env=jsdom` by default.
+This runs Jest v24.x in watch mode. See [https://jestjs.io](https://jestjs.io) for options.
 
 If you would like to disable watch mode, you can set the environment variable `CI=true`. For instance, you could set up your `package.json` `scripts` like:
 

src/templates/react.ts

@@ -19,7 +19,7 @@ const reactTemplate: Template = {
     },
     scripts: {
       ...basicTemplate.packageJson.scripts,
-      test: 'tsdx test --env=jsdom --passWithNoTests',
+      test: 'tsdx test --passWithNoTests',
     } as PackageJson['scripts'],
   },
 };