feat: warn, if LS does not match client requirements

[bastiandoetsch]

Description

Language Server & IDEs synchronize over the LsProtocolVersion. If these mismatch, functionality could be buggy or not working. This PR enables warnings to the user, if a client specifies its required protocol version:

• new setting option in InitializationOptions to transmit the required protocol version from the client
• language server checks its own protocol version, and if not the same, sends a ShowMessageRequest language server protocol dialog to the client
• the dialog contains a button to open a web browser to download either the correct & needed CLI or the standalone language server.
• The download URL takes release channels into account

Checklist

• Tests added and all succeed
• Linted
• README.md updated, if user-facing
• License file updated, if new 3rd-party dependency is introduced

🚨After having merged, please update the CLI go.mod to pull in latest language server.

Screenshots / GIFs