ci: install yarn for actions on forgejo

Summary:

The forgejo action use act under the hood. The default image does not have yarn
installed so, this is installing it.

Test Plan:

CI

.github/workflows/ci.yml

@@ -12,6 +12,9 @@ jobs:
       - name: Checkout
         uses: actions/checkout@v3
 
+      - name: Install yarn
+        run: npm i -g yarn
+
       - name: Set up Node
         uses: actions/setup-node@v3
         with:
@@ -38,6 +41,9 @@ jobs:
       - name: Checkout
         uses: actions/checkout@v3
 
+      - name: Install yarn
+        run: npm i -g yarn
+
       - name: Set up Node
         uses: actions/setup-node@v3
         with: