Update Installation Instructions to Clarify

Notes from learner:

We already discussed the slightly different installation experience for USGS Windows users and how it doesn't quite match the steps 1-13 on the prerequisite instructions page. But being new to really using Git and Git Bash, the text in the "DETAILS" section of the page also didn't quite explain exactly what I was installing. These suggested edits (or some variation) that might help clarify for the beginner reader...

e.g., This lesson will use Git and Bash.

Git is a version control system that allows you track who made changes to what, and when those changes were made. Git also has options for easily updating a shared or public version of your code on GitLab.

Bash is a commonly-used shell or command-line interpreter/interface. It is integrated and installed with Git and gives you the power to do tasks more quickly. [NOTE: I don't know if the second phrasing I added is entirely correct, but I'm trying to explain to the user that when they install Git, Bash will also be installed along with it.]

Follow the instructions below to ensure you have the proper software installed install Git (including Bash) on your computer.

And...on the 'Windows' tab, the first sentence says: "Download the Git for Windows installer from your computer’s Software Center." At first, I took that instruction literally and was searching Software Center for an application called "Git for Windows"... Instead, I eventually found "Git 2.49.0" and installed that. I also naïvely searched Software Center for 'Bash', thinking I might need to install that as a separate application. But there's no such thing in Software Center. I hoped that somehow Bash had been installed when I installed Git. So, it might make sense just to tell users to search Software Center for 'Git'.