[native] Add spoiler to pressableMarkdownTypes

Summary:
Following the stack from @ashoat, we now add spoiler to the pressableMarkdownTypes set.

Depends on D5539

Test Plan:
Check spoilers on both Android and iOS, will attach a video below.

Reviewers: ashoat, atul, ginsu

Reviewed By: ashoat

Subscribers: tomek, ashoat

Differential Revision: https://phab.comm.dev/D5779