Allow controlled overrides for <meta> tags

[DaniGuardiola]

I am resurfacing this issue as it got lost in GitHub history without a full resolution. See this issue and my comment for context: #34 (comment)

I created a proposed implementation, see the description of my PR for more details: #39

In a prior PR, Ryan questioned whether deduplication has a valid use case. I explain mine in the first linked issue, and at least two other users have a use case, discussed in this thread: #40

In that same thread, which is an alternative proposal to mine that tries to implement "better heuristics", there are some realizations that this kind of approach is, indeed, complex. One of the users even suggested that my proposal which involves explicit control by the user might be the right path.

My proposal is aligned with most of the popular meta-frameworks out there (Next.js, Nuxt, Remix, etc).

I would appreciate input on this issue from @GoodbyeNJN and @yume-chan, as they are the other users interested in fixing this. I would also be very grateful if @ryansolid (who was also involved in the conversation) and/or other active maintainers of the project could kindly look into this. I'm happy to take care of code and testing, but I need someone to get involved and offer reviews and eventual approval so it can be shipped.

I appreciate the SolidJS community and all contributors for their hard open-source work <3