`manifest.json`: `display` should be `standalone`

[riaqn]

What the title says, at

code-server/src/node/routes/vscode.ts

Line 186 in 3368ef9

display: "fullscreen",

standalone instead of fullscreen will allow hiding browser UI elements.

FWIW, in the built package, there is usr/lib/code-server/lib/vscode/resources/server/manifest.json, where display is set to standalone. But this file is not returned by the http server (don't know why).