Explain flatten(), fix wrong chap number, etc

[aofarrel]

Small text changes.

• Explains that we'll be using two different versions of mutect
• Fixes wrong chapter number
• Explains flatten(), and gives an example of how one might use it since arrays are immutable
• Fxi badd speling adn typso
• Other small clarifications

[github-actions]

⚠️ spelling errors ⚠️
There are spelling errors that need to be addressed.
Click here ➡️ for spelling errors! ❗
Add errors that aren't errors to the resources/dictionary.txt file of this repo.
If you are having troubles see this guide
Comment updated at 2024-03-27-01:28:13 with changes from e3cf21f

[github-actions]

⚠️ broken url errors ⚠️
There are broken url errors that need to be addressed.
Click here ➡️ for broken url errors! ❗
Add errors that aren't errors to the resources/ignore-urls.txt file of this repo.
If you are having troubles see this guide
Comment updated at 2024-03-27-01:28:15 with changes from e3cf21f

[github-actions]

Re-rendered previews from the latest commit:

• See preview of Bookdown here
• See preview of Coursera/Leanpub version here
• Download the preview of .docx file

Updated at 2024-03-27 with changes from e3cf21f