GHA: scan git repository and detect unvetted binary files

The only binary-looking files that are accepted in the git repository
need to match the checksums in the sha256sum file
".github/scripts/binarycheck.sums".

This is done to make sure that no one has planted any hidden (encrypted)
potentially dangerous payload in the tree.

Closes #14333

.github/workflows/binarycheck.yml

@@ -0,0 +1,23 @@
+# Copyright (C) Daniel Stenberg, <daniel@haxx.se>, et al.
+#
+# SPDX-License-Identifier: curl
+
+name: bincheck
+on:
+  push:
+    branches:
+      - master
+  pull_request:
+    branches:
+      - master
+
+permissions: {}
+
+jobs:
+  check:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@692973e3d937129bcbf40652eb9f2f61becf3332 # v4
+
+      - name: Check for binary files
+        run: ./.github/scripts/binarycheck.pl