Changed .env to .venv in README.rst

Author: evaherrada

README.rst

@@ -50,8 +50,8 @@ 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-hcsr04
 
 Usage Example