fix: handling of notification.mark_read event

[MartinCupela]

CLA

• I have signed the Stream CLA (required).
• Code changes are tested

Description of the changes, What, Why and How?

Add additional check before setting unread count for all active channels to 0. Check that the notification.mark_read event has unread_channels: 0.

[github-actions]

Size Change: +45 B (0%)

Total Size: 299 kB

Filename	Size	Change
dist/browser.es.js	65.4 kB	+8 B (0%)
dist/browser.full-bundle.min.js	35.7 kB	+6 B (0%)
dist/browser.js	66.1 kB	+10 B (0%)
dist/index.es.js	65.5 kB	+9 B (0%)
dist/index.js	66.2 kB	+12 B (0%)

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