Update README.md

Add typescript requirement in intro

README.md

@@ -4,6 +4,8 @@ Use custom tags to slice up Cypress test runs.
 
 See [cypress-tags-example](https://github.com/annaet/cypress-tags-example) for a working example.
 
+This plugin uses TypeScript to parse the tests, so you will need `typescript` installed in your project.
+
 ## Install
 
 `npm install cypress-tags`
@@ -118,4 +120,4 @@ This means that in an example test as shown below:
   it([generateTagName()], 'I will also become a wip test', () => {});
 ```
 
-The `generateTagName()` function will not resolve before the tests are filtered out. The typescript code itself will be passed into the Typescript Compiler API and the generated AST will be different to what is expected by the plugin.
+The `generateTagName()` function will not resolve before the tests are filtered out. The typescript code itself will be passed into the Typescript Compiler API and the generated AST will be different to what is expected by the plugin.