Document security risks of eavesdropping

[utopiatopia]

This is a documentations change that is supposed to resolve #1793. It not only documents what a system administrator can do in terms of reading a journal, but also includes other risks (like shoulder-surfing). Furthermore, I grouped "Plausible Deniability" and this new section together, as it seemed fitting. The risks of weak passwords bring might also belong in this section as well.

On another note, I literally don't know how to use developer tools (e.g. Git, poetry) or how collaborative projects work well enough to work on collaborative projects, so pardon me for anything I did wrong.

Checklist

• I have read the contributing doc.
• I have included a link to the relevant issue number.
• I have checked to ensure there aren't other open pull requests
  for the same issue.
• I have written new tests for these changes, as needed.

[micahellison]

Hi @utopiatopia, thanks for the PR, and congrats on your first jrnl PR! It looks great and I see nothing wrong with your process. You've documented your reasoning in the PR and explained your actions in your commit message, which is exactly what I love to see.

While previewing these docs, I thought the rather advanced "Shell History" section overshadowed the more entry-level paragraphs that followed, so I moved those paragraphs, along with your new section, up to the top. Otherwise, no notes from me, and no further action needed from you on this. The docs changes will show up with the next jrnl release.