[Static Web Assets] ZSTD compression support for SWA

The compression support is not fully fleshed/generalized and in some spots will likely assume gzip and brotli only, but I don't think it would be terrible for us to generalize things a bit to plug in an additional step.

The tasks that would need to be updated would be
https://github.com/dotnet/sdk/blob/a2a859893da48dccb8c9ea3d145225ae90d37bd6/src/StaticWebAssetsSdk/Tasks/Compression/ResolveCompressedAssets.cs#L11

Then you would also hook some target like
https://github.com/dotnet/sdk/blob/main/src/StaticWebAssetsSdk/Targets/Microsoft.NET.Sdk.StaticWebAssets.Compression.targets#L388-L409

and that should for the most part work, I think.

All those things can be packed into a nuget package (your zstd tool, and so on).