Fix: removes TODO (#1)

TODO.md

-# TODO
-
-* [ ] Support for external sources:
-  * [ ] Files with `.external.asc` extension are handled especially.
-
-  * [ ] Datas sources to be configured (`config/` folder in the keyring).
-
-  * [ ] External commands supported (such as KeePassXC CLI and
-        `password-store`).
-
-* [ ] Support for exporting data:
-  * [ ] Into `password-store`.
-
-  * [ ] Into KeePassXC files.
-
-* [ ] Support for secrets templates.
-
-* [ ] Document recommended organizational schemes for password management.
-
-* [ ] A `grep` action for filtering secret outputs.