Fix some typos and make casing more consistent

[theandrew168]

Great post! It's awesome to see how accessible this kind of software has become. Just install a few packages, download a model, and you can build some really impressive tools.

This PR addresses some minor things I found:

• basic typos
• inconsistent casing (Supervision and Inference are both stylized with capital letters)
• inconsistent punctuation (some periods at the end of code comments)

Also, VSCode auto-formatted the markdown so there are some extra newlines in the file. If those are too much of a bother, let me know and I'll make a second pass that only includes the actual bugs.

I'm hyped to read more of this type of content!

[NickHerrig]

Thanks for reading and for the feedback!