SvgXml implementation for web

[MatheusrdSantos]

Summary

Explain the motivation for making this change: here are some points to help you:

• What issues does the pull request solve? Please tag them so that they will get automatically closed once the PR is merged
  'SvgXml' for web #1279
  Attempted import error: 'SvgXml' is not exported from 'react-native-svg'. #1236

• What is the feature? (if applicable)
  This PR contains the implementation of SvgXml for web. This web implementation has exactly the same usage as the native implementation.

• How did you implement the solution?
  The web implementation relies on unstable_createElement and View from react-native-web. So, basically I used unstable_createElement to create an <svg> element with the props that comes from the XML string and set the innerHTML from the <svg> to be the XML content.
  In order to accept react-native props (the same as SvgXml native implementation), I used the <View> to wrap the <svg> and simulate the same behavior.

• What areas of the library does it impact?
  None. It just brings a new supported component for web.

Test Plan

You can check a working demo here: https://codesandbox.io/s/keen-platform-z40rg

Compatibility

OS	Implemented
iOS	✅
Android	✅
Web	✅

Checklist

• I have tested this on browser

[kofsiwon]

I hope release this quickly. I need SvgXml for react native web!!

[Sharcoux]

For those still needing this, you can try our package: @cantoo/rn-svg

[MattFoley]

@WoLewicki @MatheusrdSantos @Sharcoux Should we merge this in? It seems risky long term to have a fork maintain this functionality. Thanks!

[Sharcoux]

@MattFoley I'm glad that the project revived.

We can rebase our fork and make it ready for merge, that would be awesome. However, there is a concern you should know about:

We had to wrap the svg inside a View. This has impacts when trying to style the SVG, especially with everything related to layout. We made a system that distribute the styles between the wrapper and the svg itself, but it will very likely introduce problems in some layouts. unstable_createElement would not let us pass down every react-native props to the underlying element. Another valid approach could be to only export the element created with unstable_createElement and give up on unsupported props.

You'll find all the details here: necolas/react-native-web#1686

[MattFoley]

Hmm, I'll be honest I don't fully understand the debate on RNW, and would need more time to dive into the specifics. I also am using v14.1 of rn-svg, and don't think I can downgrade to 13. I started to rebase your fork up to v14.1 myself, but haven't finished yet, working through some BoB type errors.