docs: Bump copyright date to 2020

docs/en/conf.py

@@ -13,7 +13,7 @@ from conf_common import *  # noqa: F401, F403 - need to make available everythin
 
 # General information about the project.
 project = u'ESP-IDF Programming Guide'
-copyright = u'2016 - 2019, Espressif Systems (Shanghai) CO., LTD'
+copyright = u'2016 - 2020, Espressif Systems (Shanghai) CO., LTD'
 
 # The language for content autogenerated by Sphinx. Refer to documentation
 # for a list of supported languages.

docs/zh_CN/conf.py

@@ -13,7 +13,7 @@ from conf_common import *  # noqa: F401, F403 - need to make available everythin
 
 # General information about the project.
 project = u'ESP-IDF 编程指南'
-copyright = u'2016 - 2019 乐鑫信息科技（上海）股份有限公司'
+copyright = u'2016 - 2020 乐鑫信息科技（上海）股份有限公司'
 
 # The language for content autogenerated by Sphinx. Refer to documentation
 # for a list of supported languages.