create a proper readme

README.md

@@ -1,3 +1,30 @@
 # settingcrypt
+[![linting: pylint](https://img.shields.io/badge/linting-pylint-yellowgreen)](https://github.com/pylint-dev/pylint)
+![license: MIT](https://img.shields.io/badge/license-MIT-blue)
 
-Encrypt/decrypt setting.txt.
+
+Encrypt/decrypt setting.txt.
+
+Basically, it's an interactive Python version of the setting.txt encryption code from Wiibrew.
+
+## Usage
+
+```
+settingcrypt.py INPUT_FILE OUTPUT_FILE
+```
+
+File related parameters may be substituted with `-` to use stdin/stdout.
+
+Example:
+
+```
+settingcrypt.py setting.txt -
+```
+
+This will output a (de)crypted setting.txt to stdout.
+
+## Credit
+
+Most of this is based on [encryption code from Wiibrew](https://wiibrew.org/wiki//title/00000001/00000002/data/setting.txt#Encryption). The rest is by me.
+
+Of course, this is licensed under MIT, but if you do end up using this, credit would be much appreciated. 🙂