docs: add instructions to update corepack (#637)

Author: MikeMcC399

README.md

@@ -41,6 +41,25 @@ is distributed along with Node.js itself.
 
 </details>
 
+<details><summary>Update Corepack using npm</summary>
+
+To install the latest version of Corepack, use:
+
+```shell
+npm install -g corepack@latest
+```
+
+If Corepack was installed on your system using a Node.js Windows Installer
+`.msi` package then you might need to remove it before attempting to install a
+different version of Corepack using npm. You can select the Modify option of the
+Node.js app settings to access the Windows Installer feature selection, and on
+the "corepack manager" feature of the Node.js `.msi` package by selecting
+"Entire feature will be unavailable". See
+[Repair apps and programs in Windows](https://support.microsoft.com/en-us/windows/repair-apps-and-programs-in-windows-e90eefe4-d0a2-7c1b-dd59-949a9030f317)
+for instructions on accessing the Windows apps page to modify settings.
+
+</details>
+
 <details><summary>Install Corepack from source</summary>
 
 See [`CONTRIBUTING.md`](./CONTRIBUTING.md).