docs(examples): add runnable examples directory with 8 end-to-end bots

[victalejo]

Summary

Adds a new examples/ directory with 8 self-contained, runnable PyWa bots covering the main features of the library. Each example is a single-file main.py plus a focused README — readable in one sitting, copy-pasteable into a new project.

Today the README has good snippets, but new users still have to assemble a working webhook + tunnel + .env setup before anything runs. These examples close that gap.

What's included

#	Example	Demonstrates
01	Echo bot	Minimal FastAPI webhook + first reply
02	Menu with buttons & sections	Button, SectionList, typed CallbackData
03	Conversation with listeners	wait_for_reply / wait_for_click, timeouts, cancelers
04	Flow: newsletter signup	FlowJSON, FlowButton, on_flow_completion, RSA encryption setup
05	Templates	Create + send a marketing template with named params
06	Media handling	Receive/download images, audio, docs; send media from URL
07	Full async bot	pywa_async with async def handlers + concurrent httpx
08	Flask alternative	Same as 01, on Flask instead of FastAPI

Plus:

• examples/README.md — index, prerequisites, quick-start, troubleshooting.
• examples/.env.example — every env var any example needs.
• examples/requirements.txt — single pip install -r for all 8.

Conventions

• One main.py per example, env vars via python-dotenv (no hardcoded secrets).
• Comments explain why, not what — the code is the documentation.
• Per-example README covers WhatsApp limits, gotchas, and common Meta error codes.

[david-lev]

Hi @victalejo!

First of all, thank you so much for putting this together. I really love the clear examples you've built, and this is a massively important contribution. I am actually planning to add a pywa new <example-name> command to the new CLI that will fetch these exact examples directly from GitHub, so getting this merged is a huge priority for the project!
Since you started working on this PR, the core library has evolved a bit. Would you mind updating the examples to reflect some of our new syntax and features?

Here is what we need to tweak:

1. Drop the FastAPI Boilerplate
   We now have the pywa CLI to run and develop projects, so we no longer need the explicit FastAPI setup in the examples (users will just install "pywa[server]"). Let's remove the FastAPI code so the examples remain purely focused on Pywa logic.

2. Use the Built-in Ngrok Helper
   We recently added a handy utility to handle Ngrok tunnels automatically. Please replace the manual setup with utils.start_ngrok_tunnel:

from pywa.utils import start_ngrok_tunnel
from pywa import WhatsApp

callback_url = start_ngrok_tunnel(
    auth_token="your_ngrok_auth_token",
    domain="subdomain.ngrok-free.app",
)
wa = WhatsApp(callback_url=callback_url, ...)

3. Replace print() with Logger
   To enforce best practices, please swap out any standard print() statements in the examples for the _logger.

4. Inline Flow Components (Walrus Operator)
   To keep the code as clean as possible, we now prefer defining and placing Flow components inline using the walrus operator (:=) (see example https://pywa.readthedocs.io/en/dev/content/flows/overview.html#id2).

(e.g., Defining the button/component inline right where it is passed to the action/layout).
5. Inline Template Components
Similar to flows, please use the walrus operator (:=) for template components and use .params() directly on their component reference (see example https://pywa.readthedocs.io/en/dev/content/templates/overview.html#id8).

Thank you again for your time and effort on this! These examples are going to make the onboarding experience so much better for new developers using the CLI. Let me know if you run into any issues with the new syntax or need a hand with anything.

[david-lev]

I went ahead and updated the base branch for this PR to target dev instead of main (which is our standard workflow for new features).

To make things easier and keep everything perfectly synced, I also merged the latest dev branch directly into your fork. This means your branch now has all the latest changes and utilities we discussed above

Thanks again for this awesome contribution!