[DOC] Split the examples StringIO into the document file

Author: nobu

.rdoc_options

@@ -1,2 +1,5 @@
 ---
 main_page: README.md
+rdoc_include:
+- doc
+op_dir: html

doc/stringio/stringio.md

@@ -0,0 +1,26 @@
+\IO streams for strings, with access similar to
+{IO}[rdoc-ref:IO];
+see {IO}[rdoc-ref:IO].
+
+### About the Examples
+
+Examples on this page assume that \StringIO has been required:
+
+```
+require 'stringio'
+```
+
+And that these constants have been defined:
+
+```
+TEXT = <<EOT
+First line
+Second line
+
+Fourth line
+Fifth line
+EOT
+
+RUSSIAN = 'тест'
+DATA = "\u9990\u9991\u9992\u9993\u9994"
+```

ext/stringio/stringio.c

@@ -2133,33 +2133,7 @@ strio_set_encoding_by_bom(VALUE self)
 /*
  * :markup: markdown
  *
- * \IO streams for strings, with access similar to
- * {IO}[rdoc-ref:IO];
- * see {IO}[rdoc-ref:IO].
- *
- * ### About the Examples
- *
- * Examples on this page assume that \StringIO has been required:
- *
- * ```
- * require 'stringio'
- * ```
- *
- * And that these constants have been defined:
- *
- * ```
- * TEXT = <<EOT
- * First line
- * Second line
- *
- * Fourth line
- * Fifth line
- * EOT
- *
- * RUSSIAN = 'тест'
- * DATA = "\u9990\u9991\u9992\u9993\u9994"
- * ```
- *
+ * :include: stringio/stringio.md
  */
 void
 Init_stringio(void)