[StepSecurity] ci: Harden GitHub Actions

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

.github/workflows/build.yml

diff --git a/.github/workflows/build.yml b/.github/workflows/build.yml
index 1181762..e4bdb90 100644
--- a/.github/workflows/build.yml
+++ b/.github/workflows/build.yml
@@ -23,6 +23,9 @@
   group: ${{ github.workflow }}-${{ github.event.pull_request.number || github.ref }}
   cancel-in-progress: true
 
+permissions:
+  contents: read
+
 jobs:
   build:  
     runs-on: ubuntu-22.04