Document wxWebViewEdge build process

interface/wx/webview.h

@@ -284,10 +284,21 @@ public:
     The Edge (Chromium) backend uses Microsoft's
     <a href="https://docs.microsoft.com/en-us/microsoft-edge/hosting/webview2">Edge WebView2</a>.
     It is available for Windows 7 and newer.
-    This backend has currently a few features missing but is still
-    a better choice than IE when just displaying web content. The unsupported
-    features are the following: virtual filesystems, custom urls,
-    text selection, find, source code.
+    The following features are currently unsupported with this backend:
+    virtual filesystems, custom urls, text selection, find, source code.
+
+    This backend is not enabled by default, to build it follow these steps:
+    - Requires Visual Studio 2015 or newer
+    - Download the <a href="https://aka.ms/webviewnuget">WebView2 SDK</a>
+      nuget package (Version 0.8.355 or newer)
+    - Extract the package (it's a zip archive) to @c wxWidgets/3rdparty/webview2
+    - Enable @c wxUSE_WEBKIT_EDGE in CMake or @c setup.h
+    - Build wxWidgets webview library
+    - Copy @c WebView2Loader.dll from @c wxWidgets/3rdparty/webview2/build/
+      to your applications executable
+    - At runtime your can use wxWebView::IsBackendAvailable() to check if the
+      backend can be used (it will be available if @c WebView2Loader.dll can be
+      loaded and Edge (Chromium) is installed)
 
     @par wxWEBVIEW_WEBKIT (GTK)