Please add to the plugin documentation information regarding nuxt islands

[arsengoian]

Describe the feature

Wasn't sure how to create an issue with the documentation label. The plugins run separately for each Nuxt island, and the context of the island is available through nuxtApp.ssrContext.islandContext. I suggest a section about this behavior should be added either to the plugins page or the .server components page

Additional information

• Would you be willing to help implement this feature?
• Could this feature be implemented as a module?

Final checks

• Read the contribution guide.
• Check existing discussions and issues.

[Hebilicious]

cc @huang-julien