Chapter 1 cleanup notes ✏️

[rsese]

Ran through chapter 1, here are things I think we should update ✔️

There are other things that could be updated but tried to stick to things that are just wrong or could be confusing to a new user following along (e.g. there are more out of date screenshots but they're not out of date in a way that makes it super confusing to look at).

screenshots

https://flight-manual.atom.io/getting-started/sections/installing-atom/

• Homepage has since been updated.

https://flight-manual.atom.io/getting-started/sections/atom-basics/

• First time screenshot is out of date (missing GitHub package and Teletype items for example)

general cleanup

https://flight-manual.atom.io/getting-started/sections/installing-atom/

• Windows instructions mention "or from the Atom releases page named AtomSetup.exe", should update to mention the 64-bit version as well.

https://flight-manual.atom.io/getting-started/sections/atom-basics/

• "You can modify the active theme or install new themes by clicking on the Themes tab in the sidebar of the Settings View." is incorrect, need to go to the Install tab to install new themes.