Add tests for new features in the template that evaluates markdown syntax and finds issues- a test_markdown.py module

[lwasser]

we should test this! just writing this in the gh comment box, haven't run it, but ya since this is a template repo it makes sense for us to actually be able to test the markdown it renders, and this seems like a good opportunity to get some basic patterns in a test_markdown.py module or something

# add to test deps
import mistune

def _recursive_extract(parsed: list[dict], typ: str) -> list[dict]:
    res = []
    for block in parsed:
        if block.get('type') == typ:
            res.append(block)
        if 'children' in block:
            res.extend(_recursive_extract(block, typ))
    return res

@pytest.mark.parameterize("username", ["juno", None])
@pytest.mark.parameterize("use_git", [True, False])
def test_contributing_links(username, use_git):
    project = generated(username=username, use_git=use_git)
    contributing = (project / "CONTRIBUTING.md").read_text()
    parsed = mistune.Markdown()(contributing)
    links = _recursive_extract(parsed, "link")
    urls = [link['attrs']['url'] for link in links]
    
    if username and use_git:
        # we would also want to test for no broken links, as well as include all the links we expect to exist,
        # but just writing a quick 5 minute example
        assert f"https://github.com/{username}/alien-clones" in urls
    else:
        assert not any(["https://github.com" in url for url in urls])

Originally posted by @sneakers-the-rat in #95 (comment)