update workflows

Author: fey

.github/workflows/main.yml

@@ -10,7 +10,7 @@ jobs:
     runs-on: ubuntu-latest
 
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v6
         with:
           lfs: true
       - name: Checkout LFS objects

README.md

@@ -7,4 +7,4 @@ user: student
 password: student
 ```
 
-+
+See [Makefile](./Makefile) and [Dockerfile](./Dockerfile)