(CI): add checkout

Author: JeremyDolle

.github/workflows/w-install-dependencies.yml

@@ -6,6 +6,7 @@ jobs:
     name: Installing yarn dependencies of the project
     runs-on: ubuntu-latest
     steps:
+      - uses: actions/checkout@v2
       - name: Install yarn dependencies
         run: |
           cd template

.github/workflows/w-run-linters.yml

@@ -6,6 +6,7 @@ jobs:
     name: Run Prettier and ESLint rules checking
     runs-on: ubuntu-latest
     steps:
+      - uses: actions/checkout@v2
       - name: Run linters
         run: |
           cd template

.github/workflows/w-run-tests.yml

@@ -6,6 +6,7 @@ jobs:
     name: Run and verify jest tests
     runs-on: ubuntu-latest
     steps:
+      - uses: actions/checkout@v2
       - name: Run tests
         run: |
           cd template