docs(readme): update code examples and formatting

Add code block syntax highlighting and fix import path in documentation.

Improve readability by using proper markdown code blocks with language hints and consistent spacing throughout the documentation.

Author: tdabasinskas

README.md

@@ -37,6 +37,7 @@ Once imported, create a new Backstage API client to access different parts of Ba
 ```go
 client, err := backstage.NewClient(baseURL, "default", nil)
 ```
+
 If you want to use a custom HTTP client (for example, to handle authentication, retries or different timeouts), you can pass it as the
 third argument:
 

doc.go

@@ -5,25 +5,35 @@ Package backstage provides a client for the Backstage API.
 
 Add the package to your project as following:
 
-	import "github.com/tdabasinskas/go-backstage"
+```go
+import "github.com/datolabs-io/go-backstage/v3"
+```
 
 Once imported, create a new Backstage API client to access different parts of Backstage API:
 
-	client, err := backstage.NewClient(baseURL, "default", nil)
+```go
+client, err := backstage.NewClient(baseURL, "default", nil)
+```
 
 If you want to use a custom HTTP client (for example, to handle authentication, retries or different timeouts), you can pass it as the
 third argument:
 
-	httpClient := &http.Client{}
-	client, err := backstage.NewClient(baseURL, "default", httpClient)
+```go
+httpClient := &http.Client{}
+client, err := backstage.NewClient(baseURL, "default", httpClient)
+```
 
 The client than can be used to access different parts of the API, e.g. get the list of entities, sorted in specific order:
 
+```go
+
 	entities, response, err := c.Catalog.Entities.s.List(context.Background(), &ListEntityOptions{
-			Filters: ListEntityFilter{},
-			Fields:  []string{},
-			Order:   []ListEntityOrder{{ Direction: OrderDescending, Field: "metadata.name" },
-		},
+	        Filters: []string{},
+	        Fields:  []string{},
+	        Order:   []ListEntityOrder{{ Direction: OrderDescending, Field: "metadata.name" },
+	    },
 	})
+
+```
 */
 package backstage