add hashing

PyTeX/build/build/hashing.py

@@ -0,0 +1,12 @@
+import hashlib
+from pathlib import Path
+
+# https://stackoverflow.com/a/3431838/16371376
+
+
+def md5(file: Path):
+    hash_md5 = hashlib.md5()
+    with open(file, "rb") as f:
+        for block in iter(lambda: f.read(4096), b""):
+            hash_md5.update(block)
+        return hash_md5.hexdigest()