Dynamic import jsapi from running server

[bmingles]

Create a deephaven npm package (@deephaven/jsapi-download) that allows consuming jsapi in a non-browser context.

The jsapi code is tied to a particular running server. Non-browser clients that want to make use of the jsapi need a way to dynamically download and then import it from a running server (the vscode extension is one such consumer). Consuming the api currently requires

• Download .js files from a server
• Convert the module to a different format
  • Community serves ESM modules, but the vscode extension needs CJS modules.
  • Enterprise serves CJS modules, but some consumers may want to use ESM modules
• Polyfill WebSocket + browser apis - Colin has been working on removing browser dependencies from jsapis, so this requirement will go away soon. We'll keep the polyfill implementation outside of the scope of this ticket since it may vary for different use cases. Would be worth documenting in the README of the new package.