Added a simple usage section

Author: p-ranav

README.md

@@ -10,6 +10,7 @@
 
 - [Quick Start](#quick-start)
   * [Build Library and Standalone Sample](#build-library-and-standalone-sample)
+- [Usage](#usage)
 - [API](#api)
 - [Wildcards](#wildcards)
 - [Examples](#examples)
@@ -40,6 +41,25 @@ cmake --build build
 ./build/standalone/glob --help
 ```
 
+### Usage
+
+```cpp
+// Match on a single pattern
+for (auto& p : glob::glob("*.png")) {
+  // do something with `p`
+}
+
+// Match on multiple patterns
+for (auto& p : glob::glob({"*.png", "*.jpg"})) {
+  // do something with `p`
+}
+
+// Match recursively
+for (auto& p : glob::rglob("**/*.hpp")) {
+  // do something with `p`
+}
+```
+
 ## API
 
 * No tilde expansion is done but `*`, `?`, and character ranges expressed with `[]` will be correctly matched.