Add spoiler rule to native in fullMarkdownRules

Summary:
Add the spoiler rule for native to use the capture and parse functions from the previous diff, and return a <Text> ... </Text> React element with a spoiler style.

Linear Issue: https://linear.app/comm/issue/ENG-1983/add-spoiler-rule-to-fullmarkdownrules-in-nativemarkdownrulesreactjs

Depends on D5346

Test Plan:
Tested the spoiler text being captured with a temporary spoiler style, and I will attach the photos below. ENG-1984 will handle the styling for the spoiler text.

Example:

Reviewers: atul, ginsu, abosh, ashoat, tomek

Reviewed By: atul, ginsu, ashoat

Subscribers: ashoat, tomek

Differential Revision: https://phab.comm.dev/D5347