feat: Add kotlin lsp integration

[tjg184]

This pull request adds support for the Kotlin language server to the OpenCode LSP infrastructure. The main changes include updating language extension mappings and introducing logic to automatically download, install, and launch the Kotlin Language Server when needed.

Kotlin Language Server Integration

• Added .kt and .kts file extensions to the LANGUAGE_EXTENSIONS mapping, associating them with the Kotlin language.
• Introduced the KotlinLS entry in LSPServer, which detects the project root, checks for a local server installation, and downloads/releases the latest Kotlin Language Server from GitHub if not present. The implementation also handles platform and architecture compatibility, extraction, and launching of the server process.