Update check PR workflow

.github/workflows/check-pr.yml

@@ -1,13 +1,14 @@
-name: Do not modify index.md directly, add a file to _data/signed instead
+name: Check signatures format
 on:
   pull_request:
     branches:
       - master
     paths:
-      - index.md
+      - _data/signed/*
 jobs:
   deploy:
     runs-on: ubuntu-latest
     steps:
-      - name: Throw error
-        run: echo "Do not modify index.md directly, add a file to _data/signed instead"; exit 1
+      - uses: actions/checkout@v2
+      - name: Check signatures format
+        run: python3 check-signatures-format.py

check-signatures-format.py

@@ -0,0 +1,16 @@
+import os
+import re
+
+
+regex = re.compile(r"name: (\S+\s)*\S+\nlink: (/#|(https?://|mailto:)[a-zA-Z0-9_().@:%\+~#?&//=-]+)\n{,2}")
+
+ok = True
+for file_name in sorted(os.listdir("_data/signed")):
+    with open(f"_data/signed/{file_name}") as f:
+        contents = f.read()
+    if not re.fullmatch(regex, contents):
+        print(file_name, "has invalid format")
+        ok = False
+
+if not ok:
+    raise SystemExit(1)