New doc section: codesnippets / Advanced Examples

Presents code examples that use the instaloader module for more advanced tasks
than what is possible with the Instaloader command line interface.

Presents #46, #56, #110, #113, #120, #121.

docs/conf.py

@@ -39,7 +39,8 @@ import docs.sphinx_autodoc_typehints as sphinx_autodoc_typehints
 extensions = [
     'sphinx.ext.autodoc',
     'sphinx.ext.githubpages',
-    'sphinx.ext.intersphinx'
+    'sphinx.ext.intersphinx',
+    'sphinx.ext.extlinks'
 ]
 
 autodoc_default_flags = ['show-inheritance', 'members', 'undoc-members']
@@ -49,6 +50,8 @@ autodoc_member_order = 'bysource'
 intersphinx_mapping = {'python': ('https://docs.python.org/3', None),
                        'requests': ('http://docs.python-requests.org/en/master', None)}
 
+extlinks = {'issue': ('https://github.com/instaloader/instaloader/issues/%s', 'issue #')}
+
 # Add any paths that contain templates here, relative to this directory.
 templates_path = ['_templates']