[feat] `plugin-shell` - configure injection for links (allow disable to avoid clash with `plugin-opener`

[MGough]

Opened following discussion on Discord

If you need both plugin-shell and plugin-opener then plugin-shell will continue to manage any URLs that are 'opened'. This opening appears to be a discouraged/deprecated use of plugin-shell but there's no clear migration.

From FabianLars:

i think we have to update the shell plugin to have a setting to disable the injection like the opener plugin has