Update OnboardingView documentation (#42)

# *Update OnboardingView documentation

## ♻️ Current situation & Problem
I noticed that the documentation for the initializers and overall
descriptions of this screen were a bit unclear vague when I was trying
to use them.

**All of these changes were copied over from my previous pull request
for signed commits.**


## ⚙️ Release Notes 
N/A


## 📚 Documentation
- I added documentation to provide a coding example of the initializer
of OnboardingView, as well as a more detailed explanation.
- Also added an example fo the custom initializer



## ✅ Testing
*Please ensure that the PR meets the testing requirements set by CodeCov
and that new functionality is appropriately tested.*
*This section describes important information about the tests and why
some elements might not be testable.*


## 📝 Code of Conduct & Contributing Guidelines 

By submitting creating this pull request, you agree to follow our [Code
of
Conduct](https://github.com/StanfordSpezi/.github/blob/main/CODE_OF_CONDUCT.md)
and [Contributing
Guidelines](https://github.com/StanfordSpezi/.github/blob/main/CONTRIBUTING.md):
- [x] I agree to follow the [Code of
Conduct](https://github.com/StanfordSpezi/.github/blob/main/CODE_OF_CONDUCT.md)
and [Contributing
Guidelines](https://github.com/StanfordSpezi/.github/blob/main/CONTRIBUTING.md).

Sources/SpeziOnboarding/OnboardingView.swift

@@ -17,7 +17,12 @@ import SwiftUI
 /// - Tip: The ``SequentialOnboardingView`` provides an alternative to provide
 /// sequential information that is displayed step by step.
 ///
-/// The following example demonstrates the usage of the `OnboardingView` using its default configuration.
+/// ### Usage
+///
+/// The following example demonstrates the usage of the ``OnboardingView`` using its default configuration. The default configuration divides up
+/// each screen into sections and allows you to add a title and subtitle for the overall view itself, as well as create separate information areas. Finally,
+/// there is an option for an action that should be performed (which can be used to go to the next screen in the onboarding flow).
+///
 /// ```swift
 /// OnboardingView(
 ///     title: "Title",
@@ -39,6 +44,32 @@ import SwiftUI
 ///     // Action that should be performed on pressing the "Continue" button ...
 /// }
 /// ```
+///
+/// In implementation, you can treat the titleView, contentView, and actionView as regular SwiftUI Views. However, to simplify things, you can also use the built-in ``OnboardingTitleView`` and built-in ``OnboardingActionsView``, as demonstrated below.
+/// ``` swift
+/// OnboardingView(
+///     titleView: {
+///         OnboardingTitleView(
+///             title: "Title",
+///             subtitle: "Subtitle"
+///         )
+///     },
+///     contentView: {
+///         VStack {
+///             Text("This is the onboarding content.")
+///                 .font(.headline)
+///         }
+///     },
+///     actionView: {
+///         OnboardingActionsView (
+///             Text: "Action Text",
+///             Action: {
+///                 // Desired Action
+///             }
+///         )
+///     }
+/// )
+/// ```
 public struct OnboardingView<TitleView: View, ContentView: View, ActionView: View>: View {
     private let titleView: TitleView
     private let contentView: ContentView
@@ -70,6 +101,7 @@ public struct OnboardingView<TitleView: View, ContentView: View, ActionView: Vie
 
 
     /// Creates a customized `OnboardingView` allowing a complete customization of the  `OnboardingView`.
+    /// 
     /// - Parameters:
     ///   - titleView: The title view displayed at the top.
     ///   - contentView: The content view.