feat: add 'setup' composite action

.github/actions/setup/action.yml

@@ -0,0 +1,16 @@
+name: Setup
+description: Installs Node, Enables Corepack and caches pnpm.
+
+runs:
+  using: composite
+
+  steps:
+    - name: Enable corepack
+      run: corepack enable
+      shell: bash
+
+    - name: Setup node & pnpm
+      uses: actions/setup-node@v4
+      with:
+        node-version: lts/*
+        cache: pnpm