LSP integration: umbrella issue

[kostmo]

This issue shall gather all of the issues regarding LSP support. Creating so I can assign myself as owner.

• Implement language server OnHover handler #124
• Warn of unused variables in LSP #863
• Code lens for autocompleting inferred type signatures #980
• VSCode syntax highlighting for swarm-lang embedded within YAML #981
• Unfold function application in LSP Hover #985
• LSP warning for name shadowing #1338
• Support jump-to-definition #1764
• Format code selection in editor #1573
• Don't clear warnings in other buffers when switching between buffers #1040