added a file for the get favicon api

Author: Tochibee

specs/GetFavicon.md

@@ -0,0 +1,77 @@
+# Background
+A Favicon is an asset which is a part of every webpage, and typically displayed on each tab. Developers would
+like to have an API which allows them to retrieve the Favicon of a webpage, as well as get an update whenever
+the favicon has changed.
+
+# Description
+We propose a new Webview2 event which would allow developers to get access to the current Favicon of a page, 
+as well as be notified when the favicon changes.
+
+# Examples
+## Win32 C++ Registering a listener for favicon changes
+    ```cpp
+        CHECK_FAILURE(m_webView->add_FaviconChanged(
+            Microsoft::WRL::Callback<ICoreWebView2FaviconUpdateEventHandler>(
+            [this](ICoreWebView2* sender, IUnknown* args) -> HRESULT
+            {
+                
+                LPWSTR value;
+                CHECK_FAILURE(sender->get_FaviconUrl(&value));
+
+
+                return S_OK;
+            }
+         ).Get(),
+        &m_faviconChangedToken));  
+    ```
+## .NET / WinRT Registering a listener for favicon changes
+```c#
+webView.CoreWebView2.FaviconChanged += (CoreWebView2 sender, Object arg) =>
+{
+    string  value = sender.faviconUrl;
+
+};
+```
+# API Notes
+See [API Details](#api-details) Section below for API reference
+# API Details
+## Win32 C++
+```cpp
+/// Interface for the Favicon changed event handler
+[uuid(A0CDE626-8E5E-4EE2-9766-58F3696978FE), object, pointer_default(unique)]
+interface ICoreWebView2FaviconChangedEventHandler : IUnknown {
+  /// Called to provide the implementer with the event args for the
+  /// corresponding event.
+  HRESULT Invoke(
+      [in] ICoreWebView2* sender,
+      [in] IUnknown* args);
+}
+
+[uuid(DC838C64-F64B-4DC7-98EC-0992108E2157), object, pointer_default(unique)]
+interface ICoreWebView2_5 : ICoreWebView2_4 {
+  /// Add an event handler for the `FaviconChanged` event.
+  /// `FaviconChanged` runs when the WebView favicon changes
+  HRESULT add_FaviconChanged(
+        [in] ICoreWebView2FaviconChangedEventHandler* eventHandler,
+        [out] EventRegistrationToken* token);
+
+  /// Removing the event handler for `FaviconChanged` event
+  HRESULT remove_FaviconChanged(
+      [in] EventRegistrationToken token);
+
+  /// used to access the current value of the favicon
+  [propget] HRESULT FaviconUrl([out, retval] LPWSTR* value);
+}
+```
+
+## .Net/ WinRT
+```c#
+namespace Microsoft.Web.WebView2.Core {
+
+/// Interface for the Favicon changed event handler
+    runtimeclass CoreWebView2 {
+        event Windows.Foundation.TypedEventHandler<CoreWebView2, Object> FaviconChanged;
+        string FaviconUrl {get;};
+    }
+}
+```