feat: add support for show_deleted_message in `getMessage`

[guerinoni]

CLA

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

Description of the changes, What, Why and How?

This allow the optional query parameter show_deleted_message in API getMessage in order to show text of deleted msg.

[github-actions[bot]]

Size Change: +15 B (0%)

Total Size: 352 kB

Filename	Size	Change
dist/browser.es.js	76 kB	+3 B (0%)
dist/browser.full-bundle.min.js	46.4 kB	-1 B (0%)
dist/browser.js	76.9 kB	+5 B (0%)
dist/index.es.js	76 kB	+3 B (0%)
dist/index.js	77 kB	+5 B (0%)

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[vishalnarkhede]

@guerinoni you can merge it, I will fix the type test separately. Its not related to this PR