docs: Add custom CSS file, with code for admonition.

docs/conf.py

@@ -38,7 +38,7 @@
 ]
 
 # Add any paths that contain templates here, relative to this directory.
-#templates_path = ['templates']
+templates_path = ['templates']
 
 # The suffix of source filenames.
 source_suffix = '.rst'
@@ -144,7 +144,7 @@
 # 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']
 
 # Add any extra paths that contain custom files (such as robots.txt or
 # .htaccess) here, relative to this directory. These files are copied

docs/static/customstyle.css

@@ -0,0 +1,10 @@
+/* custom CSS for Micro Python docs
+ */
+
+.admonition-difference-to-cpython {
+    border: 1px solid black;
+}
+
+.admonition-difference-to-cpython .admonition-title {
+    margin: 4px;
+}

docs/templates/layout.html

@@ -0,0 +1,2 @@
+{% extends "!layout.html" %}
+{% set css_files = css_files + ["_static/customstyle.css"] %}