languageServerSupport
Public entry point: build the editor Extension that connects an editor for a single file to a language server through client.
Mirrors upstream @codemirror/lsp-client's languageServerSupport. It registers the LSPPlugin, server-pushed diagnostics, and server completion; the remaining feature extensions (hover, signature help, rename, etc.) are appended to the returned ExtensionList by later issues.
Return
An Extension to include in the editor state's configuration.
Parameters
client
The LSPClient wrapping the provided language server.
uri
The document URI for this editor's file.
languageId
The LSP language identifier for this file (e.g. "kotlin", "json").