Changed .env to .venv in README.rst

Author: evaherrada

README.rst

@@ -73,8 +73,8 @@ To install in a virtual environment in your current project:
 .. code-block:: shell
 
     mkdir project-name && cd project-name
-    python3 -m venv .env
-    source .env/bin/activate
+    python3 -m venv .venv
+    source .venv/bin/activate
     pip3 install adafruit-circuitpython-ds3231
 
 Usage Notes