[web] Add spoiler rule to simpleMarkdownRules
Summary:
We add the rule to web/markdown/rules.react.js in order to parse content enclosed within the || ... || characters to be spoilers. This is the web implementation of the spoiler feature.
Test Plan:
Looked at the output in the inspect element tab on a specific message that has spoiler content. For now, until the next diff, the spoiler content is enclosed within span tags, signifying that the spoiler parse rule is working.
Reviewers: atul, ginsu
Reviewed By: atul
Subscribers: ashoat, tomek, abosh
Differential Revision: https://phab.comm.dev/D5546