Docs: add more examples (composite, greyscale, tint)

docs/api-colour.md

@@ -9,7 +9,13 @@ An alpha channel may be present and will be unchanged by the operation.
 
 *   `rgb` **([string][1] | [Object][2])** parsed by the [color][3] module to extract chroma values.
 
-<!---->
+### Examples
+
+```javascript
+const output = await sharp(input)
+  .tint({ r: 255, g: 240, b: 16 })
+  .toBuffer();
+```
 
 *   Throws **[Error][4]** Invalid parameter
 
@@ -28,6 +34,12 @@ An alpha channel may be present, and will be unchanged by the operation.
 
 *   `greyscale` **[Boolean][5]**  (optional, default `true`)
 
+### Examples
+
+```javascript
+const output = await sharp(input).greyscale().toBuffer();
+```
+
 Returns **Sharp** 
 
 ## grayscale

docs/api-composite.md

@@ -46,6 +46,23 @@ and [https://www.cairographics.org/operators/][2]
 
 ### Examples
 
+```javascript
+await sharp(background)
+  .composite([
+    { input: layer1, gravity: 'northwest' },
+    { input: layer2, gravity: 'southeast' },
+  ])
+  .toFile('combined.png');
+```
+
+```javascript
+const output = await sharp('input.gif', { animated: true })
+  .composite([
+    { input: 'overlay.png', tile: true, blend: 'saturate' }
+  ])
+  .toBuffer();
+```
+
 ```javascript
 sharp('input.png')
   .rotate(180)