Update to pnpm 9 (#3741)

Author: CommandMC

.github/actions/install-deps/action.yml

@@ -8,7 +8,7 @@ runs:
         node-version: '20'
     - uses: pnpm/action-setup@v3
       with:
-        version: 8
+        version: 9
         standalone: ${{ runner.os == 'Windows' }}
     - name: Install node-gyp
       run: pnpm add --global node-gyp

README.md

@@ -212,7 +212,7 @@ Otherwise, download the file ending in .dmg from the [latest release](https://gi
 
 This part will walk you through setting up a development environment so you can build Heroic binaries yourself or make changes to the code.
 
-1. Make sure Git, NodeJS, and PNPM are installed  
+1. Make sure Git, NodeJS, and pnpm 9 are installed  
    **NOTE**: On Windows, due to an issue with electron-builder, you'll need the standalone version of pnpm (`@pnpm/exe`)
    to build packages
 2. Clone the repo and enter the cloned folder, for example with these commands: