Pinned GitHub workflows by SHA (#8334)

- Pinned actions by SHA https://github.com/ossf/scorecard/blob/main/docs/checks.md#pinned-dependencies
- Included permissions for some of the actions. https://github.com/ossf/scorecard/blob/main/docs/checks.md#token-permissions

Dependabot can upgrade pinned version of actions.

.github/workflows/docs.yaml

@@ -8,6 +8,9 @@ on:
 jobs:
 
   changes:
+    permissions:
+      contents: read  # for dorny/paths-filter to fetch a list of changed files
+      pull-requests: read  # for dorny/paths-filter to read pull requests
     runs-on: ubuntu-latest
     if: |
       (github.repository == 'kubernetes/ingress-nginx')
@@ -18,15 +21,15 @@ jobs:
     steps:
 
       - name: Checkout
-        uses: actions/checkout@v2
+        uses: actions/checkout@629c2de402a417ea7690ca6ce3f33229e27606a5 # v2
 
-      - uses: dorny/paths-filter@v2
+      - uses: dorny/paths-filter@b2feaf19c27470162a626bd6fa8438ae5b263721 # v2
         id: filter
         with:
           token: ${{ secrets.GITHUB_TOKEN }}
           filters: |
             docs:
-              - 'docs/**/*'
+             - 'docs/**/*'
 
   docs:
     name: Update
@@ -43,9 +46,9 @@ jobs:
     steps:
 
       - name: Checkout master
-        uses: actions/checkout@v2
+        uses: actions/checkout@629c2de402a417ea7690ca6ce3f33229e27606a5 # v2
 
       - name: Deploy
         uses: ./.github/actions/mkdocs
         env:
-          PERSONAL_TOKEN: "${{ secrets.GITHUB_TOKEN }}"
+          PERSONAL_TOKEN: "${{ secrets.GITHUB_TOKEN }}"