Add documentation

PasteIntoFile/RegistryUtil.cs

@@ -76,6 +76,10 @@ public static void UnRegisterApp()
         /// </summary>
         public static void RegisterApp(bool silent = false)
         {
+	        // Documentation:
+	        // https://docs.microsoft.com/en-us/windows/win32/shell/context
+	        // https://docs.microsoft.com/en-us/windows/win32/shell/context-menu
+
 	        // register "paste into file" for directory context menu
 	        foreach (var classKey in OpenClassKeys("Directory"))
 	        {

README.md

@@ -39,6 +39,23 @@ _The full changelog can be found on the [release page](https://github.com/eltos/
 
 _Tested on Windows 10_
 
+## Usage
+
+The first launch wizard will be shown when running Paste Into File for the first time after installation.
+It guides through the most important configuration.
+Further options can be accessed through the main GUI or via command line options (see below).
+
+Help is available via [GitHub discussions](https://github.com/eltos/PasteIntoFile/discussions/categories/q-a) 
+
+### Key modifiers
+
+Hold the following keys while launching Paste Into File
+- **SHIFT** inverts autosave settings once  
+  When autosave is enabled, holding SHIFT will show the dialog anyways  
+  When autosave is disabled, holding SHIFT will skip the dialog anyways
+- **CTRL** saves to a subdirectory  
+  Holding CTRL will save to an intermediate subdirectory  
+  The subfolder name supports templates and can be configured via command line options
 
 
 ## Command Line Use