ci: install yarn for actions on forgejo (#2)

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

Reviewed By: AdeAttwood

Pull Request: #2
Co-authored-by: Ade Attwood <adrian.attwood@marketdojo.com>
Co-committed-by: Ade Attwood <adrian.attwood@marketdojo.com>

.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: