Publish extension API package to npm

[wss29]

Note: we mostly implement features in the clangd language server, and rely on Microsoft's LSP client framework to expose these in VSCode. Features requiring a lot of VSCode-specific work are unlikely to be implemented.
It is necessary to publish the extension API to npm and yarn for third-party extension use, this can avoid Error: command 'clangd.applyFix' already exists
details discussed is here

[HighCommander4]

Thanks for filing. To provide some context, in #575 we added code for a new npm package in this repository called @clangd/vscode-clangd, to host the type definition files for the extension API added in that PR.

This package should be published to the npm registry, but I don't think I have the permissions to do that. I think the people who do have such permissions might be @sam-mccall and @kadircet.

As for yarn, I'm not quite sure how that works. I do see that @clangd/install shows up at https://yarnpkg.com/package?q=clangd&name=%40clangd%2Finstall; I suspect this may happen automatically (it's mirrored from npm)? If that's not the case and it requires a separate account and publishing process, then that's best discussed in a separate issue after this one is resolved.