doc: Add suricata.css to allow for some custom styling

doc/userguide/_static/css/suricata.css

@@ -0,0 +1,27 @@
+.example-rule {
+    padding: 12px 12px;
+    font-family: Consolas,"Andale Mono WT","Andale Mono","Lucida Console","Lucida Sans Typewriter","DejaVu Sans Mono","Bitstream Vera Sans Mono","Liberation Mono","Nimbus Mono L",Monaco,"Courier New",Courier,monospace;
+    font-size: 12px;
+    line-height: 1.5;
+    display: block;
+    overflow: auto;
+    color: #404040;
+
+    border: 1px solid #e1e4e5;
+    background: #fff;
+    margin: 1px 0 24px 0;
+}
+.example-rule-emphasis {
+    color: #f00;
+    font-weight: bold;
+}
+
+.example-rule-action {
+    color: #f00;
+}
+.example-rule-header {
+    color: #090;
+}
+.example-rule-options {
+    color: #00f;
+}

doc/userguide/conf.py

@@ -134,6 +134,16 @@ if not on_rtd:
         html_theme_path = [sphinx_rtd_theme.get_html_theme_path()]
     except:
         html_theme = 'default'
+    def setup(app):
+        app.add_stylesheet('css/suricata.css')
+else:
+    html_context = {
+        'css_files': [
+            'https://media.readthedocs.org/css/sphinx_rtd_theme.css',
+            'https://media.readthedocs.org/css/readthedocs-doc-embed.css',
+            '_static/css/suricata.css',
+        ],
+    }
 
 # Theme options are theme-specific and customize the look and feel of a theme
 # further.  For a list of options available for each theme, see the