Added --update param

It's being used to only update some frontmatter fields:

- title
- progress
- rate
- date

main.go

@@ -18,37 +18,38 @@ func main() {
 
 	// --media parameter
 	media := flag.String("media", "", "Specify the media type to process: movies, series, books, games, or music")
+	update := flag.Bool("update", false, "Run in update mode to update existing entries")
 	flag.Parse()
 
 	if *media == "" {
-		processAll()
+		processAll(*update)
 	} else {
 		switch *media {
 		case "movies":
-			processMovies()
+			processMovies(*update)
 		case "series":
-			processSeries()
+			processSeries(*update)
 		case "books":
-			processBooks()
+			processBooks(*update)
 		case "games":
-			processGames()
+			processGames(*update)
 		case "music":
-			processMusic()
+			processMusic(*update)
 		default:
 			fmt.Printf("Invalid media type: %s. Please use movies, series, books, games, or music.\n", *media)
 		}
 	}
 }
 
-func processAll() {
-	processMovies()
-	processSeries()
-	processBooks()
-	processGames()
-	processMusic()
+func processAll(update bool) {
+	processMovies(update)
+	processSeries(update)
+	processBooks(update)
+	processGames(update)
+	processMusic(update)
 }
 
-func processMovies() {
+func processMovies(update bool) {
 	moviesList, err := movies.LoadMovies()
 	if err != nil {
 		fmt.Printf("Error reading movies file: %v\n", err)
@@ -60,7 +61,7 @@ func processMovies() {
 	}
 }
 
-func processSeries() {
+func processSeries(update bool) {
 	seriesList, err := series.LoadSeries()
 	if err != nil {
 		fmt.Printf("Error reading series file: %v\n", err)
@@ -72,19 +73,19 @@ func processSeries() {
 	}
 }
 
-func processBooks() {
+func processBooks(update bool) {
 	booksList, err := books.LoadBooks()
 	if err != nil {
 		fmt.Printf("Error reading books file: %v\n", err)
 		return
 	}
-	err = books.ProcessBooks(booksList)
+	err = books.ProcessBooks(booksList, update)
 	if err != nil {
 		fmt.Printf("Error processing books: %v\n", err)
 	}
 }
 
-func processGames() {
+func processGames(update bool) {
 	gamesList, err := games.LoadGames()
 	if err != nil {
 		fmt.Printf("Error reading games file: %v\n", err)
@@ -96,7 +97,7 @@ func processGames() {
 	}
 }
 
-func processMusic() {
+func processMusic(update bool) {
 	albumList, err := music.LoadAlbums()
 	if err != nil {
 		fmt.Printf("Error reading music file: %v\n", err)