fix: add missing workflow permissions (#16)

Add a permission block to the workflows to limit the actions
that can be taken.

Author: patheard

.github/workflows/labels.yml

@@ -1,9 +1,13 @@
 name: Sync repository labels
+
 on:
   issues:
   pull_request:
   workflow_dispatch:
 
+permissions:
+  issues: write
+
 jobs:
   sync-labels:
     runs-on: ubuntu-latest

.github/workflows/shellcheck.yml

@@ -4,11 +4,14 @@ on:
     paths:
       - "**/*.sh"
 
+permissions:
+  contents: read
+
 jobs:
   shellcheck:
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@v2
+    - uses: actions/checkout@v6
     - name: Shellcheck
       run: |
         .github/workflows/scripts/run-shellcheck.sh