fix(Thread): parentMessage delete & initial read object

[arnautov-anton]

This PR solves three issues:

• adds handler for the reaction.updated event
• adds handler for deletion of the parent message (and itself)
• adds "patchy" placeholder read object with current user from which the unreadMessageCount can be incremented on message.new

Noteworthy changes:

• generateThread function has been renamed to generateThreadResponse
• updateParentMessageLocally takes object with message property to align with the rest of the methods
• channel "re-establishing" has been removed from the updateParentMessageLocally method, the channel has its own competences and should update its own data during applicable events

[github-actions]

Size Change: +396 B (+0.09%)

Total Size: 427 kB

Filename	Size	Change
dist/browser.es.js	92.6 kB	+83 B (+0.09%)
dist/browser.full-bundle.min.js	54.1 kB	+32 B (+0.06%)
dist/browser.js	93.8 kB	+99 B (+0.11%)
dist/index.es.js	92.7 kB	+84 B (+0.09%)
dist/index.js	93.8 kB	+98 B (+0.1%)

_{compressed-size-action}

[isekovanic]

Looks cool !