docs: how does it work and hooks

Author: huang-julien

docs/content/1.getting-started/4.How does it work.md

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+# How does it work
+
+## Server-side
+
+If enabled, nuxt-applicationinisights will load nitro-applicationinsights which also loads nitro-opentelemetry.
+
+This means the nitro server will be running Opentelemetry and [applicationinsights](https://github.com/microsoft/ApplicationInsights-node.js).
+
+## Client-side
+
+If enabled, nuxt-applicationinsights provides a plugin which initialize the [applicationinsights web sdk](https://www.npmjs.com/package/@microsoft/applicationinsights-web).
+
+## API
+
+nuxt-applicationinsights provides 2 plugins. One server side and another one client side.
+
+The client plugin provides the ApplicationInsights instance from the web SDK. And the server side one provides the default TelemetryClient that applicationinsights node initialize (it's a singleton !).
+
+Both SDK provides a similar (almost identical) API so it is easier to track any event while being in an universal component. This means you don't have to worry about whether it will work in one environment or not.

docs/content/1.getting-started/5.hooks.md

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+| name                               | type                        | Description                                                                |
+| ---------------------------------- | --------------------------- | -------------------------------------------------------------------------- |
+| `applicationinsights:config:clien` | `(config: Snippet) => void` | Called when before creating the `ApplicationInsights` instance             |
+| `applicationinsights:load:error`   | `(e: Error) => void`        | Called if something's wrong with the initialization of ApplicationInsights |
+
+## Nitro hooks
+
+See [nitro-applicationinsights](https://huang-julien-nitro-applicationinsights.nuxt.space/) and [nitro-opentelemetry](https://github.com/huang-julien/nitro-opentelemetry).