validate all asset images in CI (github#34325)

Author: Peter Bengtsson

.github/workflows/validate-asset-images.yml

@@ -0,0 +1,26 @@
+name: Validate asset images
+
+# **What it does**: Run ./script/validate-asset-images.js on all images in assets/
+# **Why we have it**: To protect from innocent and potentially malicious bad image assets
+# **Who does it impact**: Docs content.
+
+on:
+  workflow_dispatch:
+  pull_request:
+    paths:
+      - 'assets/**'
+
+permissions:
+  contents: read
+
+jobs:
+  validate-asset-images:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Check out repo
+        uses: actions/checkout@93ea575cb5d8a053eaa0ac8fa3b40d7e05a33cc8
+
+      - uses: ./.github/actions/node-npm-setup
+
+      - name: Validate all asset images
+        run: ./script/validate-asset-images.js

assets/images/enterprise/security/Enterprise-Audit-SSH-Keys.jpg renamed to assets/images/enterprise/security/Enterprise-Audit-SSH-Keys.png

@@ -43,7 +43,7 @@ fatal: The remote end hung up unexpectedly
 
 When they follow the link, they're asked to approve the keys on their account:
 
-![Auditing keys](/assets/images/enterprise/security/Enterprise-Audit-SSH-Keys.jpg)
+![Auditing keys](/assets/images/enterprise/security/Enterprise-Audit-SSH-Keys.png)
 
 After they approve or reject their keys, they'll be able interact with repositories as usual.