Respect workspace/didChangeConfiguration events

[charliermarsh]

Right now, we only support initializationOptions. But see these notes from nvim-lspconfig:

Additionally, the following options are often added:

* `init_options`: a table sent during initialization, corresponding to initializationOptions sent in [initializeParams](https://microsoft.github.io/language-server-protocol/specifications/specification-3-17/#initializeParams) as part of the first request sent from client to server during startup.
* `settings`: a table sent during [`workspace/didChangeConfiguration`](https://microsoft.github.io/language-server-protocol/specifications/specification-3-17/#didChangeConfigurationParams) shortly after server initialization. This is an undocumented convention for most language servers. There is often some duplication with initOptions.