[StepSecurity] Apply security best practices

Signed-off-by: StepSecurity Bot <bot@stepsecurity.io>

.github/workflows/check.yml

@@ -6,6 +6,9 @@ on:
   merge_group:
     branches:
     - main
+permissions:
+  contents: read
+
 jobs:
   rustfmt:
     name: rustfmt

.github/workflows/release-plz.yml

@@ -6,6 +6,9 @@ on:
 concurrency:
   group: "${{ github.workflow }}"
   cancel-in-progress: true
+permissions:
+  contents: read
+
 jobs:
   release-plz:
     name: release-plz