Update documentation on using raw HTML in dropdown

[le0tan]

What is the purpose of this pull request? (put "X" next to an item, remove the rest)

• [X] Documentation update

Resolves #1003

[yamgent]

Raw HTML in dropdown is only available since v2.9.1 (which included v2.0.1-markbind.32). Your branch was outdated so it was using v2.9.0.

I have manually rebased the branch on my local repo to verify that the changes work (not reflected in PR right now), but for future references you might want to rebase branches to the latest possible, so that future reviewers will be able to easily check your changes, without having to locally checkout your branch.

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On another note, I realised that dropdown has never supported any form of markdown at all. Therefore, we weren't able to do something like this:

<dropdown text="**Strong text**" type="warning">

I am raising this because should markdown be accepted, then there's really no reason why we should encourage the authors to follow the examples actually, since it diverts them away from using markdown syntax, and asking them to use raw HTML instead.

I am wondering whether we should seek to implement markdown in dropdown, and introduce slots to allow additional customization, rather than just supporting raw HTML like now. @ang-zeyu what do you think?

[le0tan]

#1029
@yamgent I made the suggested implementation, if it looks OK I'll write documentation to that in the new PR and you may close this PR.

[ang-zeyu]

I am wondering whether we should seek to implement markdown in dropdown, and introduce slots to allow additional customization

Sounds good; 👍

I don't think we should include any extra slots, since the design of dropdowns aren't suited for containing much other than inline markdown. Though, I may've yet to think of a use case for it.

[le0tan]

PR closed due to more updated version at #1029