replaced npm with pnpm in some installs

Author: FranciscoMoretti

packages/notion-client/readme.md

@@ -11,7 +11,7 @@
 ## Install
 
 ```bash
-npm install notion-client
+pnpm install notion-client
 ```
 
 This package is compatible with server-side V8 contexts such as Node.js, Deno, and Cloudflare Workers.

packages/notion-types/readme.md

@@ -11,7 +11,7 @@
 ## Install
 
 ```bash
-npm install notion-types
+pnpm install notion-types
 ```
 
 This package only exports types and is compatible with both Node.js and browsers.

packages/notion-utils/readme.md

@@ -11,7 +11,7 @@
 ## Install
 
 ```bash
-npm install notion-utils
+pnpm install notion-utils
 ```
 
 This package is compatible with both Node.js and client-side web usage.