Add support for GIF output using cgif in prebuilt binaries

lib/constructor.js

@@ -13,7 +13,7 @@ const debuglog = util.debuglog('sharp');
 /**
  * Constructor factory to create an instance of `sharp`, to which further methods are chained.
  *
- * JPEG, PNG, WebP, AVIF or TIFF format image data can be streamed out from this object.
+ * JPEG, PNG, WebP, GIF, AVIF or TIFF format image data can be streamed out from this object.
  * When using Stream based output, derived attributes are available from the `info` event.
  *
  * Non-critical problems encountered during processing are emitted as `warning` events.
@@ -246,6 +246,9 @@ const Sharp = function (input, options) {
     webpNearLossless: false,
     webpSmartSubsample: false,
     webpReductionEffort: 4,
+    gifBitdepth: 8,
+    gifEffort: 7,
+    gifDither: 1,
     tiffQuality: 80,
     tiffCompression: 'jpeg',
     tiffPredictor: 'horizontal',