simplify tutorial

- remove steps that are probably not necessary (e.g., checking systemd
from PowerShell)
- reduces complexity in web app (e.g., no CSS)
- provides an example of what VSCode offers (e.g., snippets)
- shortens section on interoperability (e.g., focus on terminal-based
moving of image from Windows)
- increase emphasis on built-in tooling at the start
- favour terminal commands over GUI where appropriate (e.g., Windows
terminal keybinding, instead of chevron)
- avoid confusing naming ("UbuntuWSL" is not a helpful name for the web
project)
- various small fixes and adjustments

Author: edibotopic