Add pnpm install and run scripts to Development doc (#199)

* Update development.mdx

Add pnpm install instructions to the development documentation. As well as alternative instructions for using run scripts instead of installing the Mintlify package globally.

* specify mintlify in pnpm up

---------

Co-authored-by: Ronan McCarter <[email protected]>

Author: frankievalentine

development.mdx

@@ -17,9 +17,13 @@ description: 'Preview changes locally to update your docs'
   npm i -g mintlify
   ```
 
-```bash yarn
-yarn global add mintlify
-```
+  ```bash yarn
+  yarn global add mintlify
+  ```
+
+  ```bash pnpm
+  pnpm add -g mintlify
+  ```
 
 </CodeGroup>
 
@@ -29,6 +33,27 @@ yarn global add mintlify
 mintlify dev
 ```
 
+Alternatively, if you do not want to install Mintlify globally you can use a run script available:
+
+<CodeGroup>
+  ```bash npm
+  npx mintlify dev
+  ```
+
+  ```bash yarn
+  yarn dlx mintlify dev
+  ```
+
+  ```bash pnpm
+  pnpm dlx mintlify dev
+  ```
+
+</CodeGroup>
+
+<Warning>
+  Yarn's "dlx" run script requires yarn version >2. See [here](https://yarnpkg.com/cli/dlx) for more information.
+</Warning>
+
 A local preview of your documentation will be available at `http://localhost:3000`.
 
 ### Custom Ports
@@ -55,9 +80,13 @@ Please note that each CLI release is associated with a specific version of Mintl
   npm i -g mintlify@latest
   ```
 
-```bash yarn
-yarn global upgrade mintlify
-```
+  ```bash yarn
+  yarn global upgrade mintlify
+  ```
+
+  ```bash pnpm
+  pnpm up --global mintlify
+  ```
 
 </CodeGroup>