doc: Update README.md. (#19)

Author: MinoruSekine

README.md

@@ -1,3 +1,26 @@
 # win-toast-cli
 
-Invoke toast notification by output of another application.
+Invoke toast notification by command-line.
+
+## Usage
+
+On PowerShell console,
+
+```powershell
+> toast-cli.ps1 -body "Body message"
+```
+
+### Options
+
+- `-body string`: String for toast notification body
+- `-title string`: String for toast notification title (optional)
+- `-detail string`: String for toast notification detail (optional)
+- `-?`: Show help
+
+## Contents
+
+- `toast-cli.ps1`: PowerShell script to show toast notification
+- `toast-cli.cmd`: Batch wrapper to `toast-cli.ps1`.
+  This makes easy to invoke from command prompt.
+- `tools/toast-scoop-status.ps1`:
+  Sample tool to show application updates installed by [scoop](https://scoop.sh)