//This also allows you to set up a keybinding for Add all missing imports:
{
    "key": "ctrl+shift+i",
    "command": "editor.action.sourceAction",
    "args": {
        "kind": "source.addMissingImports",
        "apply": "first"
    }
}

// Or even enable Add all missing imports on save:

"editor.codeActionsOnSave": [
    "source.addMissingImports"
]