bimi needs a special svg file to be valid

[markvantilburg]

See this url for more information

https://bimigroup.org/using-the-rnc-schema-to-validate-bimi-svg-images/

[markvantilburg]

image validator:
https://bimigroup.org/resources/SVG_PS-latest.rnc.txt

[markvantilburg]

rnc could be converted to xsd using this tool: https://relaxng.org/jclark/trang.html
Then we could use that XSD to validate the svg file

[TheIndra55]

A couple of thoughts while quickly looking into this while working on #5.

To validate the SVG file we need to fetch it, there's a synchronous Send method on HttpClient but it's not supported on .NET Standard 2.0, so that will either require to make all methods asynchronous or add the latest System.Net.Http as dependency.

We also need a way to mock these requests in our tests, so we can have test cases without hosting all these files.