Use the same XSLT engine as Firefly

[mwilliamson-firefly]

As alluded to in #59, is there any reason not to use the same XSLT engine as Firefly? This would make discrepancies between how things work in the pattern library when being served and in Firefly less likely, and would make writing extensions much easier (if we decided to do so, which is a whole other discussion).

[dkhuntrods]

I couldn't see any way to do this in a cross platform way; suggestions welcome.

[roobottom]

+1 on this if possible.

[mwilliamson-firefly]

I was hoping that the XSLT engine was included in .NET Core, but that doesn't seem to be the case yet. I'll try to see if that's likely to be the case any time soon.

[mwilliamson-firefly]

Here's the relevant issue: https://github.com/dotnet/corefx/issues/5593

So, probably not possible without a bit of work at the moment, but might be easier in the future.

[dkhuntrods]

Keep an eye on that so, and plan to migrate once it's possible.