chore: Set permissions for GitHub actions

Restrict the GitHub token permissions only to the required ones; this way, even if the attackers will succeed in compromising your workflow, they won’t be able to do much.

- Included permissions for the action. https://github.com/ossf/scorecard/blob/main/docs/checks.md#token-permissions

https://docs.github.com/en/actions/using-workflows/workflow-syntax-for-github-actions#permissions

https://docs.github.com/en/actions/using-jobs/assigning-permissions-to-jobs

[Keeping your GitHub Actions and workflows secure Part 1: Preventing pwn requests](https://securitylab.github.com/research/github-actions-preventing-pwn-requests/)

Signed-off-by: nathannaveen <42319948+nathannaveen@users.noreply.github.com>

.github/workflows/docker.yml

@@ -1,6 +1,9 @@
 name: Docker
 on: [pull_request]
 
+permissions:
+  contents: read
+
 jobs:
   build:
     runs-on: ubuntu-latest

.github/workflows/tests.yml

@@ -7,6 +7,9 @@ on:
     branches-ignore:
       - i18n_master
 
+permissions:
+  contents: read
+
 jobs:
   tests:
     runs-on: ubuntu-18.04
@@ -60,6 +63,8 @@ jobs:
           name: screenshots
           path: tmp/screenshots
   coveralls:
+    permissions:
+      contents: none
     runs-on: ubuntu-18.04
     needs: tests
     env: