feat: inline duplicate properties

[cossssmin]

This PR introduces a new option, inlineDuplicateProperties, which allows the user to choose whether Juice should inline the same property multiple times on the same element, instead of only inlining the winning/highest specificity selector.

This option is false by default, you need to opt-in to the functionality.

The use-case is particularly for HTML emails, where progressive enhancement is sometimes required because not all email clients support the same level of CSS features. For example, given this Tailwind CSS example:

<div class="bg-black bg-black/50" />

... with inlineDuplicateProperties: true we can get this output:

<div style="background-color: #000; background-color: rgba(0,0,0,0.5)" />

... which will show a solid black background color in clients such as Outlook on Windows, which do not support rgba.

---

Closes #380

[cossssmin]

@jrit not sure if you want to review?

[jrit]

no qualms from me, I defer to your decisions @cossssmin

[cossssmin]

Thanks man, I have one more idea for a feature and I also want to look into #387, then we can do a feature release. And after that I can look into the cheerio/undici thing, to update that dependency too and do a major release (since cheerio now needs Node 18).