Update README.md with tsconfig.json

packages/gatsby-plugin-typescript/README.md

@@ -2,29 +2,35 @@
 Provides drop-in support for TypeScript and TSX.
 
 ## Install
-`yarn add gatsby-plugin-typescript ts-loader typescript`
+`yarn add gatsby-plugin-typescript typescript`
 
 ## How to use
 1. Include the plugin in your `gatsby-config.js` file.
-2. Write your components in TSX or TypeScript.
-3. You're good to go.
+1. Add `tsconfig.json` file on your root directory.
+1. Write your components in TSX or TypeScript.
+1. You're good to go.
 
+`gatsby-config.js`
 ```javascript
-// in gatsby-config.js
 plugins: [
-  // no configuration
   `gatsby-plugin-typescript`,
-  // custom configuration
-  {
-    resolve: `gatsby-plugin-typescript`,
-    options: {
-      // compilerOptions are passed directly to the compiler
-      compilerOptions: {
-        target: `esnext`,
-        experimentalDecorators: true,
-        jsx: `react`
-      }
-    }
-  }
 ]
+```
+
+`tsconfig.json`
+```json
+{
+    "compilerOptions": {
+        "outDir": "./dist/",
+        "sourceMap": true,
+        "noImplicitAny": true,
+        "module": "commonjs",
+        "target": "esnext",
+        "jsx": "react",
+        "lib": ["dom", "es2015", "es2017"]
+    },
+    "include": [
+        "./src/**/*"
+    ]
+}
 ```