Was "removing" (rather not re-applying) the `[spoiler]` BBCode because we were testing the **whole** class of the `span`/`div` was `spoiled` but we added another class and thus broke this functionnality.
In order to fix this issue, the test to determine whether a `span`/`div` is a spoiler, now uses a regular expression to check whether the `class` **contains** the word `spoiled`.
Reference - https://meta.discourse.org/t/quoting-spoiler-text-doesnt-include-spoiler-tags-in-the-quote/170145
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