workflows: add permissions block

We'd like to run GitHub Actions with the least possible permissions
assigned to the token for security reasons.  To make this possible,
let's add a permissions block to each workflow that lacks one.

Author: bk2204

.github/workflows/lint.yml

@@ -12,6 +12,9 @@ on:
       - go.mod
       - go.sum
 
+permissions:
+  contents: read
+
 jobs:
   lint:
     runs-on: ubuntu-latest

.github/workflows/test.yml

@@ -1,6 +1,8 @@
 ---
 on: [push, pull_request]
 name: Test
+permissions:
+  contents: read
 jobs:
   test:
     strategy: