feat(ui): add custom scrollbaar to dashboard

[sanukadevx]

Add custom scrollbar styling to dashboard.

[calesthio]

The actual feature here is straightforward and makes sense: this PR is just adding custom scrollbar styling to the dashboard in dashboard/public/jarvis.html.

What needs cleanup before merge:

• package-lock.json has a large unrelated diff that does not appear to be caused by the scrollbar change itself
• the branch is also dirty against current master

Please rebase/update the branch and remove the unrelated package-lock.json churn so the PR stays scoped to the UI change.

[calesthio]

I haven't been able to get to this yet because work has been busy, but I definitely plan to review it over the weekend.