Add NLP Tutorial

[henrifroese]

This builds upon

• Fix type checks to not fail if first value in series is NaN/missing. #174 (the tutorial does not work otherwise - really important)
• Doctests fail with new Black version. #171

TODO

• add references at the end to the other tutorials

EDIT:

You can now see the tutorial with the images right here. Will switch images to higher res. as some are a little blurry. Apart from that, I'm interested in opinions content- and style-wise 🤞

[jbesomi]

Looks good! 👍

Review:

• For the DF output, it would be elegant if you just copy-paste the output as we are doing in the getting-started (See "Getting Started" section, for instance, >>> df.head(2) )
• This will need to go under website/blog as this is a Tutorial blog post and not a "getting started" page
• Try to have subsection shorter and eventually add a sub-sub section.
• "Of course, we use Texthero's count_sentences function.". Is "Of course" pertinent?

Extra:

• We will need to adapt a bit the CSS code for the code snippet, it does not look that good (but that's not related with this PR)

Example:

Count Sentences - Who is the most well-known superhero?

Becomes

Count Sentences

Who is the most well-known superhero?

[henrifroese]

Incorporated the suggested changes from both your reviews 🪂 .

This will need to go under website/blog as this is a Tutorial blog post and not a "getting started" page

I believe that this should be getting-started-nlp (We accidentally named it tutorial-nlp) as this showcases the nlp module and tutorials should probably be more focused and in-depth (e.g. "Sparsity" or "Topic Modelling")