Add pydantic to dependency list of the package

[turing4ever]

Describe the bug
after pip install the package, you would have to install pydantic manually.
You forgot to add pydantic as a dependency

Fix
Add one line here: https://github.com/lvxhnat/pyetfdb-scraper/blob/master/setup.py#L40

        "pydantic",

[turing4ever]

You also need

"lxml"