Intend to implement: window/progress

Created by: felixfbecker

For TypeScript dependency installation it would be useful to report progress, so we can answer requests without needing to do ugly heuristics.

Here's what the Rust language server already sends:

https://github.com/rust-lang-nursery/rls/blob/0e7432a4ff58bf3584c44bdb390d557cee846968/src/lsp_data.rs#L366-L393

LSP issue: https://github.com/Microsoft/language-server-protocol/issues/70 LSP proposal: https://github.com/Microsoft/language-server-protocol/pull/245 vscode-languageserver-node PR that implements what Rust sends: https://github.com/Microsoft/vscode-languageserver-node/pull/261/files#diff-663e3c81ec938b18f2ab1cd4b47055f0R21 (we could copy the protocol/src/protocol.progress.proposed.ts file for our use cases)

This needs an extension API for reporting progress, like https://code.visualstudio.com/docs/extensionAPI/vscode-api#window.withProgress

@francisschmaltz could you help with designing this?