[Bug] The error for not having Jinja installed is confusing

[shaib]

Describe the bug
If you start out with Sanic and install sanic[ext], then try to use templating before installing Jinja2, you get a confusing error which may make you think that Sanic itself is broken.

I had a fairly trivial example, for a template using a request parameter
(irrelevant lines removed)

from sanic import Sanic

app = Sanic("ShaiApp")

@app.get("/room/<room_name>")
@app.ext.template("room.html")
async def handler(request: Request):
    return {"room_name": room_name}

This was in server.py. Trying to run it without Jinja installed yielded:

$ sanic server:app 
Traceback (most recent call last):
  File "/home/shai/.virtualenvs/sanic3.10/bin/sanic", line 8, in <module>
    sys.exit(main())
  File "/home/shai/.virtualenvs/sanic3.10/lib/python3.10/site-packages/sanic/__main__.py", line 12, in main
    cli.run(args)
  File "/home/shai/.virtualenvs/sanic3.10/lib/python3.10/site-packages/sanic/cli/app.py", line 106, in run
    app = self._get_app(app_loader)
  File "/home/shai/.virtualenvs/sanic3.10/lib/python3.10/site-packages/sanic/cli/app.py", line 175, in _get_app
    app = app_loader.load()
  File "/home/shai/.virtualenvs/sanic3.10/lib/python3.10/site-packages/sanic/worker/loader.py", line 78, in load
    module = import_module(self.module_name)
  File "/usr/lib/python3.10/importlib/__init__.py", line 126, in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
  File "<frozen importlib._bootstrap>", line 1050, in _gcd_import
  File "<frozen importlib._bootstrap>", line 1027, in _find_and_load
  File "<frozen importlib._bootstrap>", line 1006, in _find_and_load_unlocked
  File "<frozen importlib._bootstrap>", line 688, in _load_unlocked
  File "<frozen importlib._bootstrap_external>", line 883, in exec_module
  File "<frozen importlib._bootstrap>", line 241, in _call_with_frames_removed
  File "/home/shai/sanic/server.py", line 13, in <module>
    @app.ext.template("room.html")
  File "/home/shai/.virtualenvs/sanic3.10/lib/python3.10/site-packages/sanic_ext/bootstrap.py", line 210, in template
    return self.templating.template(template_name, **kwargs)
AttributeError: 'Extend' object has no attribute 'templating'. Did you mean: 'template'?

Expected behavior
I'd expect an error saying something like "you need a templating library installed". Something to make it clear that it's me doing something wrong, not the framework.

Environment (please complete the following information):

• OS: Debian testing (currently trixie)
• Version 23.3.0