docs: darker output

Author: henryiii

docs/_static/css/custom.css

@@ -0,0 +1,3 @@
+.highlight .go {
+  color: #707070;
+}

docs/conf.py

@@ -157,7 +157,11 @@
 # 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 = []
+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