FTL VSCode extension

[wesbillman]

• Create extension and lsp client in ts (https://github.com/TBD54566975/ftl-vscode)
• Only start ftl dev if we're in an FTL project
• Add FTL server output to bottom panel

Future enhancements to be worked on later after initial LSP work is out.

• Add side panel for FTL extension (could have buttons to restart the server)
• Add webview for showing FTL events (maybe graph too)?

[alecthomas]

Oooh is this published somewhere?!

[wesbillman]

Not published yet, but will do! TBD54566975/ftl-vscode#5

In the meantime, I'll update the README.md on that other repo (I wonder if we want the extension in our ftl repo at some point 🤔)