Improve github action security

See https://docs.github.com/en/actions/writing-workflows/choosing-what-your-workflow-does/controlling-permissions-for-github_token

.github/workflows/benchmark.yml

@@ -1,5 +1,7 @@
 name: Benchmark
 
+permissions: {}
+
 on:
   push:
     branches:

.github/workflows/codeql.yml

@@ -11,6 +11,8 @@
 #
 name: "CodeQL"
 
+permissions: {}
+
 on:
   push:
     branches: [ develop, next ]

.github/workflows/docker.yml

@@ -1,5 +1,7 @@
 name: Docker
 
+permissions: {}
+
 on:
   push:
     branches:

.github/workflows/nightly.yml

@@ -1,5 +1,7 @@
 name: Nightly
 
+permissions: {}
+
 on:
   schedule:
     - cron: '0 3 * * *'

.github/workflows/stats.yml

@@ -1,5 +1,7 @@
 name: Stats
 
+permissions: {}
+
 on:
   push:
     branches:

.github/workflows/test.yml

@@ -1,5 +1,7 @@
 name: Test
 
+permissions: {}
+
 on:
   push:
   pull_request: