Clarify email address requirement for ssh-keygen -C in Episode 7

[gjduine]

How could the content be improved?

Problem

The example in Episode 7, line 206 shows:

$ ssh-keygen -t ed25519 -C "a.linguini@ratatouille.fr"

For beginners, it's unclear whether the email must be their GitHub account email or if any email works.

Suggested Improvement
Add a note clarifying that the -C flag adds a comment/label to identify the key:

Note: The email address in the -C option is used as a label to identify this SSH key. Use the email address associated with your GitHub account so you can easily remember which key belongs to which account.

This will help new learners choose the correct email without confusion.

### Which part of the content does your suggestion apply to?

episode 7 in git-novice

[erinmgraham]

Hi @gjduine, thank you for raising this issue - it's good to be thinking about beginner clarity.

You’re absolutely right that the -C flag is used to add a comment/label to the SSH key. One important nuance, though, is that there isn’t a required or correct email to use there. The official documentation doesn't prescribe what to use here and while many people, including us, use their github email address because it's convenient, others may use hostnames, the key's purpose, or no comment at all.

Taking that into consideration, can I ask you to revise your suggested improvement text and submit it as a PR for review?

[gjduine]

OK, I just submitted a PR