Update README and add helloworld example

examples/helloworld/main.go

@@ -0,0 +1,20 @@
+package main
+
+import (
+	"fmt"
+
+	"github.com/charmbracelet/glamour"
+)
+
+func main() {
+	in := `# Hello World
+
+This is a simple example of glamour!
+Check out the other [other examples](https://github.com/charmbracelet/glamour/tree/master/examples).
+
+Bye!
+`
+
+	out, _ := glamour.Render(in, "dark")
+	fmt.Printf(out)
+}