maint: set base permissions for all workflows

.github/workflows/devcontainer-build.yml

@@ -17,6 +17,8 @@ concurrency:
   group: "${{ github.workflow }}"
   cancel-in-progress: true
 
+permissions:
+  contents: read
 
 jobs:
   build-and-push:

.github/workflows/packages-cleanup.yml

@@ -28,6 +28,9 @@ on:
 env:
   PACKAGE_NAME: "freqtrade"
 
+permissions:
+  contents: read
+
 jobs:
   deploy-docker:
     name: "Delete Packages"