Bump actions/checkout from 2.3.5 to 2.4.0 (#43)

Author: dependabot[bot]

.github/workflows/dockerimage.yml

@@ -9,7 +9,7 @@ jobs:
     runs-on: ubuntu-latest
 
     steps:
-    - uses: actions/checkout@v2.3.5
+    - uses: actions/checkout@v2.4.0
       with:
         fetch-depth: '0'
     - id: tagName