refactor: Replace yarn with pnpm

Author: davidkna-sap

.devcontainer/devcontainer.json

@@ -35,7 +35,7 @@
   // },
 
   // Use 'postCreateCommand' to run commands after the container is created.
-  "postCreateCommand": "yarn install --ignore-engines --frozen-lockfile",
+  "postCreateCommand": "pnpm install --frozen-lockfile",
 
   // Comment out connect as root instead. More info: https://aka.ms/vscode-remote/containers/non-root.
   "remoteUser": "node"