fix!: rename plugin to vitestWebContainers

[AriPerkkio]

• Renames vitestWebcontainers to vitestWebContainers.

Migration:

- import { vitestWebcontainers } from "@webcontainer/test/plugin";
+ import { vitestWebContainers } from "@webcontainer/test/plugin";

[pkg-pr-new]

Open in StackBlitz

npm i https://pkg.pr.new/@webcontainer/test@17

commit: ab43fc1