Add description of GitHub subset.

README.md

@@ -158,6 +158,14 @@ This dataset is in English (`EN`).
 }
 ```
 
+#### github
+```
+{
+  'text': "/* filesystem.c\n * Filesystem utility routines\n *\n * Wireshark - Network traffic analyzer\n * By Gerald Combs <gerald@wireshark.org>\n * Copyright 1998 Gerald Combs\n *\n * SPDX-License-Identifier: GPL-2.0-or-later\n */\n\n#include <config.h>\n\n#include <stdio.h>\n#include <stdlib.h>\n#include <string.h>\n#include <errno.h>\n\n#include <glib.h>...",
+  'meta': "{'repo_name': 'wireshark/wireshark', 'stars': '2789', 'repo_language': 'C', 'file_name': 'packet-mpeg-audio-template.c', 'mime_type': 'text/x-c'}"
+}
+```
+
 ### Data Fields
 
 #### all
@@ -212,6 +220,11 @@ This dataset is in English (`EN`).
 - `meta` (str): Metadata of the data instance with: bibliographic_information, source_file, abstract, classifications, 
   inventors.
 
+#### github
+
+- `text` (str): Text.
+- `meta` (str): Metadata of the data instance with: repo_name, stars, repo_language, file_name, mime_type.
+
 ### Data Splits
 
 The "all" configuration is composed of 3 splits: train, validation and test.