Initial commit

Spun out from where I had it previously (a private repo) and tidied the
code up a bit. Included a bit more static analysis courtesy of ruff,
and fixed up the errors. (There weren't many.)

Update README

README.md

@@ -0,0 +1,17 @@
+# pdf_decrypt
+
+A tool to decrypt annoyingly encrypted PDFs.
+
+Save passwords in `~/.config/pdf_decrypt/passwords.yaml` as a list, like so:
+
+```yaml
+---
+- 12345
+- 54321
+```
+
+The script will go through each of them and try to decrypt it. If none of them
+work, it will exit and complain.
+
+I suggest installing through `uv`, this makes this script into an executable
+on your path. If you prefer, there is also PEP-723 metadata inline.