fix(ci): add missing SPDX headers to workflow files

.github/workflows/codeql.yml

@@ -1,3 +1,4 @@
+# SPDX-License-Identifier: MPL-2.0
 # For most projects, this workflow file will not need changing; you simply need
 # to commit it to your repository.
 #

.github/workflows/generator-generic-ossf-slsa3-publish.yml

@@ -1,3 +1,4 @@
+# SPDX-License-Identifier: MPL-2.0
 # This workflow uses actions that are not certified by GitHub.
 # They are provided by a third-party and are governed by
 # separate terms of service, privacy policy, and support

.github/workflows/pages.yml

@@ -1,3 +1,4 @@
+# SPDX-License-Identifier: MPL-2.0
 name: GitHub Pages (Ddraig SSG)
 on:
   push:

.github/workflows/php.yml

@@ -1,3 +1,4 @@
+# SPDX-License-Identifier: MPL-2.0
 name: PHP Composer
 
 on:

.github/workflows/rust.yml

@@ -1,3 +1,4 @@
+# SPDX-License-Identifier: MPL-2.0
 name: Rust
 
 on: