added missing output function documentation

docs/reference/cag_option_print.md

@@ -0,0 +1,28 @@
+---
+title: cag_option_print
+description: Prints all options to the terminal.
+---
+
+_(since v1.0.0)_  
+description: Prints all options to the terminal.
+
+## Description
+```c
+void cag_option_print(const cag_option *options, size_t option_count,
+  FILE *destination);
+```
+
+This function prints all options to the terminal. This can be used to generate
+the output for a "--help" option.
+ 
+## Parameters
+ * **options**: The options which will be printed.
+ * **option_count**: The option count which will be printed.
+ * **destination**: The destination where the output will be printed.
+
+
+## Changelog
+
+| Version    | Description                                            |
+|------------|--------------------------------------------------------|
+| **v1.0.0** | The function is introduced.                            |

docs/reference/index.md

@@ -21,3 +21,10 @@ Gets the value from the option.
 
 * **[cag_option_get_index]({{ site.baseurl }}{% link reference/cag_option_get_index.md %})**  
 Gets the current index of the context.
+
+## Output
+This section describes functions which are used to output argument information.
+
+### Functions
+* **[cag_option_print]({{ site.baseurl }}{% link reference/cag_option_print.md %})**  
+Prints all options to the terminal.

include/cargs.h

@@ -52,8 +52,8 @@ typedef struct cag_option_context
 /**
  * @brief Prints all options to the terminal.
  *
- * This function prints all options to the terminal. This is used to generate
- * the output for a "--help" option.
+ * This function prints all options to the terminal. This can be used to
+ * generate the output for a "--help" option.
  *
  * @param options The options which will be printed.
  * @param option_count The option count which will be printed.