Update to-do list example in `?` menu about zulip

[zulipbot]

Hello @zulip/server-user-docs members, this issue was labeled with the "area: documentation (user)" label, so you may want to check it out!

[alya]

@N-Shar-ma FYI, in case you'd like to take care of this one.

[ilyesskhayati]

@zulipbot claim

[zulipbot]

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[ilyesskhayati]

I completed it! Here's the final version on my server.

@alya can you please review this? Thank you