Update docs and changelog with pro features

CHANGELOG.md

@@ -5,6 +5,7 @@
 - `IMGPROXY_NETWORK` config. Allows to bind on Unix socket.
 - `IMGPROXY_CACHE_CONTROL_PASSTHROUGH` config.
 - `imgproxy health` command.
+- (pro) `IMGPROXY_GIF_OPTIMIZE_FRAMES` & `IMGPROXY_GIF_OPTIMIZE_TRANSPARENCY` configs and `gif_options` processing option.
 
 ### Fixed
 - Fix detection of SVG starting with a comment.

docs/configuration.md

@@ -104,6 +104,11 @@ Also you may want imgproxy to respond with the same error message that it writes
 * `IMGPROXY_PNG_QUANTIZE`: when true, enables PNG quantization. libvips should be built with libimagequant support. Default: false;
 * `IMGPROXY_PNG_QUANTIZATION_COLORS`: maximum number of quantization palette entries. Should be between 2 and 256. Default: 256;
 
+### Advanced GIF compression
+
+* `IMGPROXY_GIF_OPTIMIZE_FRAMES`: <img class="pro-badge" src="assets/pro.svg" alt="pro" /> when true, enables GIF frames optimization. This may produce a smaller result, but may increase compression time.
+* `IMGPROXY_GIF_OPTIMIZE_TRANSPARENCY`: <img class="pro-badge" src="assets/pro.svg" alt="pro" /> when true, enables GIF transparency optimization. This may produce a smaller result, but may increase compression time.
+
 ## WebP support detection
 
 imgproxy can use the `Accept` HTTP header to detect if the browser supports WebP and use it as the default format. This feature is disabled by default and can be enabled by the following options:

docs/generating_the_url_advanced.md

@@ -368,6 +368,15 @@ pngo:%png_interlaced:%png_quantize:%png_quantization_colors
 
 Allows redefining PNG saving options. All arguments have the same meaning as [Advanced PNG compression](configuration.md#advanced-png-compression) configs. All arguments are optional and can be omitted.
 
+#### GIF options <img class="pro-badge" src="assets/pro.svg" alt="pro" />
+
+```
+gif_options:%gif_optimize_frames:%gif_optimize_transparency
+gifo:%gif_optimize_frames:%gif_optimize_transparency
+```
+
+Allows redefining GIF saving options. All arguments have the same meaning as [Advanced GIF compression](configuration.md#advanced-gif-compression) configs. All arguments are optional and can be omitted.
+
 #### Preset
 
 ```