Add support for handling did change configuration to the ruby-lsp

[vinistock]

We allow users to configure the desired features from the VS Code plugin. However, it currently requires starting the LSP for the configuration changes to take effect.

We can use the didChangeConfiguration notification to verify if a feature has been enabled or disabled and then notify the client by unregistering or registering a capability without requiring a full restart.

Documentation: https://microsoft.github.io/language-server-protocol/specifications/lsp/3.17/specification/#workspace_didChangeConfiguration

[vinistock]

These notifications have actually been deprecated in favour of a pull model (i.e.: the server asking the client for specific configurations).

In that new model, I don't think this is feasible, so we might just need to continue restarting the server when a configuration is changed.