RSX parser suggestion, iteration 2

Hi, original author of [syn-rsx](https://github.com/stoically/syn-rsx) had created [an issue about using generic crate](https://github.com/DioxusLabs/dioxus-html-macro/issues/1) for html parsing.

Since then, original author disappeared, and i have created a fork https://github.com/stoically/syn-rsx/issues/58
and wanted to share it with you.

In order to check if there is any interest in generalizing (ht/x)ml template parsing for rust.

Brief view shows that one feature is currently incompatible with this macro.
- string literal in place of attribute keys is not supported by [rstml](https://github.com/rs-tml/rstml). (but rstml support blocks on attribute level, and dash separated idents (like x-foo-bar) )

It also contain few improvements that could be interested:
- support unquoted text (on stable without spaces- can be used for script/jscode)
- recovery parsing - allows you to keep semantic feature (like highlight, or goto definition) when some errors in user code exist.