Expand document width to better fit 120 character examples.

Author: HexDecimal

docs/_static/css/custom.css

@@ -0,0 +1,3 @@
+.wy-nav-content {
+    max-width: 60em
+}

docs/conf.py

@@ -169,7 +169,9 @@
 # Add any paths that contain custom static files (such as style sheets) here,
 # relative to this directory. They are copied after the builtin static files,
 # so a file named "default.css" will overwrite the builtin "default.css".
-# html_static_path = ['_static']
+html_static_path = ["_static"]
+
+html_css_files = ["css/custom.css"]
 
 # Add any extra paths that contain custom files (such as robots.txt or
 # .htaccess) here, relative to this directory. These files are copied