Docs - add vs expose extensions

[urbiz-grafana]

Fixes https://github.com/grafana/grafana-community-team/issues/311.

Previews:

• https://grafana-dev.com/developers/plugin-tools/reference/ui-extensions
• https://grafana-dev.com/developers/plugin-tools/reference/extensions-add-expose

[github-actions]

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[andresmgot]

Some comments here, treat this as a user reading this docs more than a developer of the feature 😅 (you may need to wait for someone more knowledgeable person about this topic)

[andresmgot]

I think it would be better to have a real example here, I don't think this is close to any real usage (at least that I can find). I tried looking for addPanel* or something similar in our code base and found nothing.

You may need to wait for some expert on extensions to be available but based on the current documentation I think, that for defining an extension point, you need to use for example usePluginComponents as explained here.

Then, you can add a component to the new extension point (as explained here).

Maybe I am completely off and addLink and addComponent are more complex scenarios that were not the goal to be explained here but if that's the case we should probably clarify that.