update docs and examples for pyproject

setup.py -> pyproject.toml
venv -> .venv

docs/tutorial/layout.rst

@@ -41,7 +41,7 @@ The project directory will contain:
 * ``flaskr/``, a Python package containing your application code and
   files.
 * ``tests/``, a directory containing test modules.
-* ``venv/``, a Python virtual environment where Flask and other
+* ``.venv/``, a Python virtual environment where Flask and other
   dependencies are installed.
 * Installation files telling Python how to install your project.
 * Version control config, such as `git`_. You should make a habit of
@@ -80,8 +80,8 @@ By the end, your project layout will look like this:
     │   ├── test_db.py
     │   ├── test_auth.py
     │   └── test_blog.py
-    ├── venv/
-    ├── setup.py
+    ├── .venv/
+    ├── pyproject.toml
     └── MANIFEST.in
 
 If you're using version control, the following files that are generated
@@ -92,7 +92,7 @@ write. For example, with git:
 .. code-block:: none
     :caption: ``.gitignore``
 
-    venv/
+    .venv/
 
     *.pyc
     __pycache__/