doc: add update-register usage

Author: jorisre

README.md

@@ -38,6 +38,8 @@ This will start an interactive wizard, and then run the specified transform.
 
 Update the `register` API inside a component which use `useForm` of React Hook Form. This transform is not applied if the component doesn't use `useForm`.
 
+    npx @hookform/codemod v7/update-register
+
 <details>
     <summary>Examples</summary>
 

transforms/v7/register.ts

@@ -9,7 +9,11 @@ export default function transformer(file: FileInfo, api: API, options) {
     trailingComma: true
   };
 
-  // We search for all `import { ... } from "react-hook-form"`
+  /**
+   * We search for all react-hook-form's imports
+   * @example
+   *  import { ... } from "react-hook-form"
+   * */
   const reactHookFormImports = root.find(j.ImportDeclaration, {
     source: { value: REACT_HOOK_FORM }
   });