add README

README.md

@@ -0,0 +1,19 @@
+```python
+from pyrohlik import Rohlk
+```
+
+```python
+client = Rohlik("API_KEY")
+```
+
+```python
+product = client.get_product(1362825)
+```
+
+```python
+orders = client.get_orders()
+```
+
+```python
+recipe = client.get_recipe(59)
+```