feat(bookstack-api-02m): create example code in examples/ directory

Add three example programs: basic (list books, get page), search
(full-text search with CLI args), and export (markdown/PDF export).

examples/search/main.go

@@ -0,0 +1,47 @@
+// Search example: search for content and display results.
+package main
+
+import (
+	"context"
+	"fmt"
+	"log"
+	"os"
+
+	bookstack "code.beautifulmachines.dev/jakoubek/bookstack-api"
+)
+
+func main() {
+	if len(os.Args) < 2 {
+		fmt.Fprintf(os.Stderr, "Usage: %s <search query>\n", os.Args[0])
+		os.Exit(1)
+	}
+
+	client, err := bookstack.NewClient(bookstack.Config{
+		BaseURL:     os.Getenv("BOOKSTACK_URL"),
+		TokenID:     os.Getenv("BOOKSTACK_TOKEN_ID"),
+		TokenSecret: os.Getenv("BOOKSTACK_TOKEN_SECRET"),
+	})
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	ctx := context.Background()
+	query := os.Args[1]
+
+	results, err := client.Search.Search(ctx, query, &bookstack.ListOptions{Count: 10})
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	fmt.Printf("Search results for %q:\n\n", query)
+	for i, r := range results {
+		fmt.Printf("%d. [%s] %s (score: %.1f)\n", i+1, r.Type, r.Name, r.Score)
+		if r.Preview != "" {
+			fmt.Printf("   %s\n", r.Preview)
+		}
+	}
+
+	if len(results) == 0 {
+		fmt.Println("No results found.")
+	}
+}