ci: restrict token permissions and add badges to README.md

Change-Id: I057fab1370f4f3941bf3fe1de9c6d99198e3bd71
diff --git a/.github/workflows/docs.yml b/.github/workflows/docs.yml
index adccec2..9f25475 100644
--- a/.github/workflows/docs.yml
+++ b/.github/workflows/docs.yml
@@ -1,9 +1,14 @@
 name: Docs
 on:
   push:
-  pull_request:
+    paths-ignore:
+      - '.mailmap'
+      - '.travis.yml'
   workflow_dispatch:
 
+permissions:
+  contents: read
+
 jobs:
   build:
     strategy: