docs: install cypress via pnpm

docs/guides/getting-started/installing-cypress.mdx

@@ -6,7 +6,7 @@ title: Installing Cypress
 
 ## <Icon name="graduation-cap" /> What you'll learn
 
-- How to install Cypress via `npm` or `yarn`
+- How to install Cypress via `npm`、`yarn` or `pnpm`
 - How to install Cypress via direct download
 - How to version and run Cypress via `package.json`
 
@@ -78,6 +78,35 @@ yarn add cypress --dev
 System proxy properties `http_proxy`, `https_proxy` and `no_proxy` are respected
 for the download of the Cypress binary.
 
+### <Icon name="terminal" /> `pnpm install`
+
+Installing Cypress via [`pnpm`](https://pnpm.io/):
+
+```shell
+git clone https://github.com/cypress-io/github-action
+```
+
+Clone Cypress's GitHub Action repository to the current directory. This will create a folder called "github-action" and copy the contents of the repository into it.
+
+```shell
+cd github-action/examples/basic-pnpm
+```
+
+`/basic-pnpm` will be the location of the later example code.
+
+```shell
+pnpm install --frozen-lockfile && pnpm run test
+```
+
+Install the dependencies and run the test cases in the project
+
+:::info
+
+You need to make sure that you have the `pnpm` environment installed locally.
+If not you need to install it: `npm install pnpm@latest -g`.
+
+:::
+
 ### <Icon name="download" /> Direct download
 
 If you're not using Node or `npm` in your project or you want to try Cypress out