docs: update readme

README.md

@@ -3,3 +3,25 @@
 Simple CLI that lets users hide secret messages in PNGs. Made for learning purposes.
 
 Access to the tutorial followed [here](https://picklenerd.github.io/pngme_book/introduction.html).
+
+## Usage
+
+#### Encode a message:
+`./pngme encode <png path> <chunk type> <message> <output path (optional)>`
+
+Ex: `./pngme encode ./image.png ruSt "psst, this is a secret"`
+
+#### Decode a message:
+`./pngme decode <png path> <chunk type>`
+
+Ex: `./pngme decode ./image.png ruSt`
+
+#### Remove a message:
+`./pngme remove <png path> <chunk type>`
+
+Ex: `./pngme remove ./image.png ruSt`
+
+#### Print the chunks information:
+`./pngme print <png path>`
+
+Ex: `./pngme print ./image.png`