Build libnode and publish nuget packages

[jasongin]

For embedding Node.js, we need to build libnode binaries for each supported platform, and publish the binaries as native nuget packages.

Until the Node API embedding PR is merged, we'll need to build from a fork. And, it may require manually merging the PR changes into the target version of Node.js. I did that for Node.js v19.9 and v20.0 already:
https://github.com/jasongin/nodejs/tree/napi-libnode-v19.9.0
https://github.com/jasongin/nodejs/tree/napi-libnode-v20.0.0

(I tried to backport to v18, but the PR changes depended on significant updates in v19.)

Edit: Instructions for building libnode are at https://microsoft.github.io/node-api-dotnet/scenarios/dotnet-js.html

[vmoroz]

I am going to work on implementing an ADO pipeline to publish libnode as a Nuget package.

[ShortDevelopment]

Are there already nuget packages for libnode or can I download the binaries somewhere?

[jasongin]

Not yet. @vmoroz was working on that but got busy with other priorities.

[jasongin]

Update: This is the latest known good branch for building a libnode that works with this project:
https://github.com/jasongin/nodejs/tree/napi-libnode-v20.9.0