Update upgrading.md (#31173)

Include required steps for the latest React and Next.js version upgrade via npm/yarn.



## Bug

- [ ] Related issues linked using `fixes #number`
- [ ] Integration tests added
- [ ] Errors have helpful link attached, see `contributing.md`

## Feature

- [ ] Implements an existing feature request or RFC. Make sure the feature request has been accepted for implementation before opening a PR.
- [ ] Related issues linked using `fixes #number`
- [ ] Integration tests added
- [ ] Documentation added
- [ ] Telemetry added. In case of a feature if it's used or not.
- [ ] Errors have helpful link attached, see `contributing.md`

## Documentation / Examples

- [x] Make sure the linting passes by running `yarn lint`

docs/upgrading.md

@@ -10,6 +10,34 @@ description: Learn how to upgrade Next.js.
 
 The minimum Node.js version has been bumped from 12.0.0 to 12.22.0 which is the first version of Node.js with native ES Modules support.
 
+### Upgrade React version to latest
+
+To upgrade you can run the following command:
+
+```
+npm install react@latest react-dom@latest
+```
+
+Or using `yarn`:
+
+```
+yarn add react@latest react-dom@latest
+```
+
+### Upgrade Next.js version to 12
+
+To upgrade you can run the following command in the terminal:
+
+```
+npm install next@12
+```
+
+or
+
+```
+yarn add next@12
+```
+
 ### SWC replacing Babel
 
 Next.js now uses Rust-based compiler [SWC](https://swc.rs/) to compile JavaScript/TypeScript. This new compiler is up to 17x faster than Babel when compiling individual files and up to 5x faster Fast Refresh.