pip install missing in chapter 04 and chapter 06 jupyter notebooks docs

[bmerkle]

Is your feature request related to a problem? Please describe. for chapter 04 and 06 the pip install tiktoken is missing. Should we add this to the docs ? We could also add a requirements.txt so that there is code for getting the packages and not only doc

It seems that tiktoken also requires rust compiler on the machine to build the libs, at least this was necessary in my case.

Describe the solution you'd like I could update the docs accordingly

@koreyspace