feat(docs): add URL generation examples and authentication parameters to README

Author: manu4543

README.md

@@ -89,6 +89,203 @@ await client.files.upload({ file: await toFile(Buffer.from('my bytes'), 'file'),
 await client.files.upload({ file: await toFile(new Uint8Array([0, 1, 2]), 'file'), fileName: 'fileName' });
 ```
 
+## URL generation
+
+The ImageKit SDK provides a powerful `helper.buildSrc()` method for generating optimized image and video URLs with transformations. Here are examples ranging from simple URLs to complex transformations with overlays and signed URLs.
+
+### Basic URL generation
+
+Generate a simple URL without any transformations:
+
+```ts
+import ImageKit from '@imagekit/nodejs';
+
+const client = new ImageKit({
+  privateAPIKey: process.env['IMAGEKIT_PRIVATE_API_KEY'],
+  password: process.env['ORG_MY_PASSWORD_TOKEN'],
+});
+
+// Basic URL without transformations
+const url = client.helper.buildSrc({
+  urlEndpoint: 'https://ik.imagekit.io/your_imagekit_id',
+  src: '/path/to/image.jpg'
+});
+// Result: https://ik.imagekit.io/your_imagekit_id/path/to/image.jpg
+```
+
+### URL generation with transformations
+
+Apply common transformations like resizing, cropping, and format conversion:
+
+```ts
+// URL with basic transformations
+const transformedUrl = client.helper.buildSrc({
+  urlEndpoint: 'https://ik.imagekit.io/your_imagekit_id',
+  src: '/path/to/image.jpg',
+  transformation: [
+    {
+      width: 400,
+      height: 300,
+      crop: 'maintain_ratio',
+      quality: 80,
+      format: 'webp'
+    }
+  ]
+});
+// Result: https://ik.imagekit.io/your_imagekit_id/path/to/image.jpg?tr=w-400,h-300,c-maintain_ratio,q-80,f-webp
+```
+
+### URL generation with image overlay
+
+Add image overlays to your base image:
+
+```ts
+// URL with image overlay
+const imageOverlayUrl = client.helper.buildSrc({
+  urlEndpoint: 'https://ik.imagekit.io/your_imagekit_id',
+  src: '/path/to/base-image.jpg',
+  transformation: [
+    {
+      width: 500,
+      height: 400,
+      overlay: {
+        type: 'image',
+        input: '/path/to/overlay-logo.png',
+        position: {
+          x: 10,
+          y: 10
+        },
+        transformation: [
+          {
+            width: 100,
+            height: 50
+          }
+        ]
+      }
+    }
+  ]
+});
+// Result: URL with image overlay positioned at x:10, y:10
+```
+
+### URL generation with text overlay
+
+Add customized text overlays:
+
+```ts
+// URL with text overlay
+const textOverlayUrl = client.helper.buildSrc({
+  urlEndpoint: 'https://ik.imagekit.io/your_imagekit_id',
+  src: '/path/to/base-image.jpg',
+  transformation: [
+    {
+      width: 600,
+      height: 400,
+      overlay: {
+        type: 'text',
+        text: 'Sample Text Overlay',
+        position: {
+          x: 50,
+          y: 50,
+          focus: 'center'
+        },
+        transformation: [
+          {
+            fontSize: 40,
+            fontFamily: 'Arial',
+            fontColor: 'FFFFFF',
+            typography: 'b'  // bold
+          }
+        ]
+      }
+    }
+  ]
+});
+// Result: URL with bold white Arial text overlay at center position
+```
+
+### URL generation with multiple overlays
+
+Combine multiple overlays for complex compositions:
+
+```ts
+// URL with multiple overlays (text + image)
+const multipleOverlaysUrl = client.helper.buildSrc({
+  urlEndpoint: 'https://ik.imagekit.io/your_imagekit_id',
+  src: '/path/to/base-image.jpg',
+  transformation: [
+    {
+      width: 800,
+      height: 600,
+      overlay: {
+        type: 'text',
+        text: 'Header Text',
+        position: { x: 20, y: 20 },
+        transformation: [{ fontSize: 30, fontColor: '000000' }]
+      }
+    },
+    {
+      overlay: {
+        type: 'image',
+        input: '/watermark.png',
+        position: { focus: 'bottom_right' },
+        transformation: [{ width: 100, opacity: 70 }]
+      }
+    }
+  ]
+});
+// Result: URL with text overlay at top-left and semi-transparent watermark at bottom-right
+```
+
+### Signed URLs for secure delivery
+
+Generate signed URLs that expire after a specified time for secure content delivery:
+
+```ts
+// Generate a signed URL that expires in 1 hour (3600 seconds)
+const signedUrl = client.helper.buildSrc({
+  urlEndpoint: 'https://ik.imagekit.io/your_imagekit_id',
+  src: '/private/secure-image.jpg',
+  transformation: [
+    {
+      width: 400,
+      height: 300,
+      quality: 90
+    }
+  ],
+  signed: true,
+  expiresIn: 3600  // URL expires in 1 hour
+});
+// Result: URL with signature parameters (?ik-t=timestamp&ik-s=signature)
+
+// Generate a signed URL that doesn't expire
+const permanentSignedUrl = client.helper.buildSrc({
+  urlEndpoint: 'https://ik.imagekit.io/your_imagekit_id',
+  src: '/private/secure-image.jpg',
+  signed: true
+  // No expiresIn means the URL won't expire
+});
+// Result: URL with signature parameter (?ik-s=signature)
+```
+
+### Authentication parameters for client-side uploads
+
+Generate authentication parameters for secure client-side file uploads:
+
+```ts
+// Generate authentication parameters for client-side uploads
+const authParams = client.helper.getAuthenticationParameters();
+console.log(authParams);
+// Result: { token: 'uuid-token', expire: timestamp, signature: 'hmac-signature' }
+
+// Generate with custom token and expiry
+const customAuthParams = client.helper.getAuthenticationParameters('my-custom-token', 1800);
+console.log(customAuthParams);
+// Result: { token: 'my-custom-token', expire: 1800, signature: 'hmac-signature' }
+```
+
+These authentication parameters can be used in client-side upload forms to securely upload files without exposing your private API key.
+
 ## Handling errors
 
 When the library is unable to connect to the API,