docs: inform about using with typescript (#325)

packages/core/README.md

@@ -178,3 +178,7 @@ Or using the Sass helper:
 ```html
 <button class="ods-button -action--primary round">Round Button</button>
 ```
+
+Components have basic types exported so that you could create your own JS/TS variations using any renderer chosen (for example, Vue or Angular).
+
+Please note that the `@onfido/castor-icons` package is a peer dependency and is required to be installed for **types** to work properly. Yarn and newer versions of npm (using lockfile v2) will resolve it, otherwise it must be installed manually even if you don't plan to use icons.

packages/react/README.md

@@ -58,6 +58,14 @@ You may wish to configure your bundler to transpile to a different module syntax
 
 For example, you might choose UMD module syntax targeting ES5 if your app needs to support IE11 (please note that Castor is not tested in Internet Explorer).
 
+### Use with TypeScript
+
+Components extend base prop types with JSX additions.
+
+When using with TypeScript, always import types from `@onfido/castor-react`.
+
+Please note that the `@onfido/castor-icons` package is a peer dependency and is required to be installed for **types** to work properly. Yarn and newer versions of npm (using lockfile v2) will resolve it, otherwise it must be installed manually even if you don't plan to use icons.
+
 ### Make custom styled components
 
 You should use props for each component modifier, but it is also possible to create custom styled components.