ci: replace Travis with GitHub Actions

Sync docs/conf.py with ndn-cxx

Change-Id: I2c7106ef52a0e7c00de6767c6b59dbd3ce1dc082
diff --git a/docs/conf.py b/docs/conf.py
index 5fa4789..05d0f76 100644
--- a/docs/conf.py
+++ b/docs/conf.py
@@ -1,10 +1,8 @@
-# -*- coding: utf-8 -*-
-#
 # Configuration file for the Sphinx documentation builder.
 #
 # This file only contains a selection of the most common options. For a full
 # list see the documentation:
-# http://www.sphinx-doc.org/en/master/config
+# https://www.sphinx-doc.org/en/master/usage/configuration.html
 
 # -- Path setup --------------------------------------------------------------
 
@@ -20,13 +18,13 @@
 # -- Project information -----------------------------------------------------
 
 project = u'ChronoSync: A Synchronization Protocol for NDN'
-copyright = u'Copyright © 2012-2020 Regents of the University of California.'
+copyright = u'Copyright © 2012-2021 Regents of the University of California.'
 author = u'Named Data Networking Project'
 
-# The short X.Y version
+# The short X.Y version.
 #version = ''
 
-# The full version, including alpha/beta/rc tags
+# The full version, including alpha/beta/rc tags.
 #release = ''
 
 # There are two options for replacing |today|: either, you set today to some
@@ -40,12 +38,13 @@
 
 # If your documentation needs a minimal Sphinx version, state it here.
 #
-needs_sphinx = '1.1'
+needs_sphinx = '1.3'
 
 # Add any Sphinx extension module names here, as strings. They can be
 # extensions coming with Sphinx (named 'sphinx.ext.*') or your custom
 # ones.
 extensions = [
+    'sphinx.ext.extlinks',
     'sphinx.ext.todo',
 ]
 
@@ -86,6 +85,12 @@
 # so a file named "default.css" will overwrite the builtin "default.css".
 html_static_path = ['_static']
 
+html_copy_source = False
+html_show_sourcelink = False
+
+# Disable syntax highlighting of code blocks by default.
+highlight_language = 'none'
+
 
 # -- Options for LaTeX output ------------------------------------------------
 
@@ -132,3 +137,7 @@
 doxylink = {
     'ChronoSync': ('ChronoSync.tag', 'doxygen/'),
 }
+
+extlinks = {
+    'issue': ('https://redmine.named-data.net/issues/%s', 'issue #'),
+}