docs: update readme

README.md

@@ -1,3 +1,22 @@
 # random-pseudonyme-generator
 
-Generate funny random pseudonym
+Generate funny random pseudonyms composed of an adjective, a noun and a number between 1 and 999.
+
+## Usage
+
+You can either use python to directly run the script like this : 
+
+```bash
+python pyrpg.py $NUMBER_OF_PSEUDONYMS
+```
+
+Or you can use the provided Dockerfile to build a docker image and run it like this : 
+
+```bash
+docker build -t pyrpg .
+docker run --volume $(pwd)/out:/out --env NUMBER_OF_PSEUDONYMS=$NUMBER_OF_PSEUDONYMS pyrpg
+```
+
+If you don't proivide a number of pseudonyms, the script will generate 100 by default.
+
+Pseudonyms are written to a file named `pseudonyms.txt` in and 'out' volume so you can retrieve them easily.