docs: update README.md with info for the libs tag

Author: sis0k0

README.md

@@ -1,10 +1,18 @@
 TypeScript support for NativeScript projects
 =======================================
 
-How to use
+# How to use
 ----------
 ```
-$ tns install typescript
+$ npm install -D nativescript-dev-typescript
 ```
 
 The above command installs this module and installs the necessary hooks. TypeScript compilation happens when the project is prepared for build. A file named `tsconfig.json` that specifies compilation options will be created in the project folder and should be committed to source control.
+
+# Note for plugins
+----------
+```
+$ npm install -D nativescript-dev-typescript@libs
+```
+
+When developing NativeScript plugins, you should install the 'libs' tag of the nativescript-dev-typescript plugin. This will skip adding 'paths' mappings for 'tns-core-modules' in the 'tsconfig.json', because of this Angular compiler [issue](https://github.com/angular/angular-cli/issues/5618).