Support LSP workspace/didChangeConfiguration in addition to initializationOptions #2180

Currently custom LSPs can only be configured with initialize which passes initializationOptions as part of the LSP initialization call.
Some LSP servers require settings to be passed in workspace/didChangeConfiguration instead. (Namely tailwindcss-language-server is what I'm running into at the moment)

workspace/didChangeConfiguration appears to be the more standard way to configuring LSP servers (Neovim passes settings as this, which the majority of configurations in nvim-lspconfig utilize as opposed to of init_options).