Add SPDX license header check workflow

.github/workflows/spdx.yml

@@ -0,0 +1,32 @@
+name: SPDX License Check
+
+on:
+  pull_request:
+    paths:
+      - "pyproject.toml"
+      - "src/**"
+      - ".github/workflows/spdx.yml"
+  push:
+    paths:
+      - "pyproject.toml"
+      - "src/**"
+      - ".github/workflows/spdx.yml"
+  workflow_dispatch:
+
+permissions:
+  contents: read
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true
+
+jobs:
+  spdx:
+    name: check spdx headers
+    runs-on: ubuntu-latest
+    steps:
+      - name: checkout
+        uses: actions/checkout@v6
+      - uses: enarx/spdx@d4020ee98e3101dd487c5184f27c6a6fb4f88709 # master
+        with:
+          licenses: MIT

src/bookmeterjson/__init__.py

@@ -0,0 +1 @@
+# SPDX-License-Identifier: MIT

src/bookmeterjson/__main__.py

@@ -1,3 +1,5 @@
+# SPDX-License-Identifier: MIT
+
 import argparse
 import sys
 

src/bookmeterjson/config.py

@@ -1,3 +1,5 @@
+# SPDX-License-Identifier: MIT
+
 from dataclasses import dataclass, field
 from pathlib import Path
 

src/bookmeterjson/models.py

@@ -1,3 +1,5 @@
+# SPDX-License-Identifier: MIT
+
 from __future__ import annotations
 
 from dataclasses import dataclass

src/bookmeterjson/scraper.py

@@ -1,3 +1,5 @@
+# SPDX-License-Identifier: MIT
+
 from __future__ import annotations
 
 import contextlib