feat: README file

README.md

@@ -1,4 +1,17 @@
 # A function plotter in python
 
 A recreational programming project.
+
 The idea is to implement a simple math expression language and simple features to plot functions.
+
+For now a simple matplotlib based implementation is provided.
+
+Example:
+
+```
+from plotter.matplotlib import plot_expression
+
+plot_expression("sin(x) * 2^(3*x)", start=-10.0, stop=10.0, increment=0.1)
+```
+
+![Function plotted in the [-10.0, 10.0] range with 0.1 increments](./plot_example.png)