Update FAQ and command line.

docs/command-line-options.md

@@ -24,9 +24,14 @@ Specify which set of predefined plugins to use. If this option is not used, and
 `--config <CONFIG>`  
 Custom configuration file.
 
+<a id="enable"></a>
 `--enable <plugin...>`  
 Specify one or more builtin plugins to run in addition to those specified by `--preset` or `--config`.
 
+<a id="options"></a>
+` --options <FILENAME>`  
+Path to a [JSON file](https://www.json.org) containing configuration parameters for enabled plugins. The JSON file should contain an object whose keys are the names of plugins, and whose values are the parameters to pass to that plugin.
+
 `--disable <plugin...>`  
 Specify one or more plugins specified by `--preset` or `--config` which should not be run.
 

docs/faq.md

@@ -4,6 +4,8 @@ Compression
 
 - [Just remove whitespace from a file](#comp-ws)
 - [Run a single plugin](#comp-1plugin)
+- [Round decimal values](#comp-round)
+- Change the default options for a plugin
 
 ## Compression
 
@@ -26,3 +28,33 @@ Use `preset-none`. For example:
 ```
 npx svgo-ll --preset none -i test.svg
 ```
+
+<a id="comp-round"></a>
+
+### Round decimal values
+
+Rounding is not enabled by default. To enable the rounding plugin, use the [`--enable` command line option](./command-line-options.md#enable). For example, to add rounding to the default plugins:
+
+```
+npx svgo-ll -i test.svg --enable round
+```
+
+<a id="comp-defaults"></a>
+
+### Change the default options for a plugin
+
+You can change the default options for a plugin by creating a JSON file and using the [`--options` command line option](./command-line-options.md#options). For example, to use the default plugins and specify an id that should not be changed by the `cleanupIds` plugin, create file named `options.json` with the content:
+
+```
+{
+  "cleanupIds": {
+    "preserve": "abc"
+  }
+}
+```
+
+and use the command:
+
+```
+npx svgo-ll -i test.svg --options options.json
+```