docs: Update docs with setProviderAndWait

Signed-off-by: Fabrizio Demaria <[email protected]>

Author: fabriziodemaria

README.md

@@ -76,23 +76,18 @@ and in the target dependencies section add:
 ```swift
 import OpenFeature
 
-// Configure your custom `FeatureProvider` and pass it to OpenFeatureAPI
-let customProvider = MyCustomProvider()
-OpenFeatureAPI.shared.setProvider(provider: customProvider)
-
-// Configure your evaluation context and pass it to OpenFeatureAPI
-let ctx = MutableContext(
-    targetingKey: userId,
-    structure: MutableStructure(attributes: ["product": Value.string(productId)]))
-OpenFeatureAPI.shared.setEvaluationContext(evaluationContext: ctx)
-
-// Get client from OpenFeatureAPI and evaluate your flags
-let client = OpenFeatureAPI.shared.getClient()
-let flagValue = client.getBooleanValue(key: "boolFlag", defaultValue: false)
+Task {
+    let provider = CustomProvider()
+    // configure a provider, wait for it to complete its initialization tasks
+    await OpenFeatureAPI.shared.setProviderAndWait(provider: provider)
+
+    // get a bool flag value
+    let client = OpenFeatureAPI.shared.getClient()
+    let flagValue = client.getBooleanValue(key: "boolFlag", defaultValue: false)
+    ...
+}
 ```
 
-Setting a new provider or setting a new evaluation context might trigger asynchronous operations (e.g. fetching flag evaluations from the backend and store them in a local cache). It's advised to not interact with the OpenFeature client until the `ProviderReady` event has been sent (see [Eventing](#eventing) below).
-
 ## 🌟 Features
 
 
@@ -118,9 +113,11 @@ If the provider you're looking for hasn't been created yet, see the [develop a p
 Once you've added a provider as a dependency, it can be registered with OpenFeature like this:
 
 ```swift
-OpenFeatureAPI.shared.setEvaluationContext(evaluationContext: ctx)
+await OpenFeatureAPI.shared.setProviderAndWait(provider: MyProvider())
 ```
 
+> Asynchronous API that doesn't wait is also available
+
 ### Targeting
 
 Sometimes, the value of a flag must consider some dynamic criteria about the application or user, such as the user's location, IP, email address, or the server's location.