Use dark mode for code preview if user prefers `prefers-color-scheme: dark`

pystencils currently does not look good in dark mode :/

pystencils/cpu/cpujit.py

@@ -176,8 +176,14 @@ def read_config():
         ('clear_cache_on_start', False),
     ])
 
+    default_highlight_style = OrderedDict([
+        ('light_theme', 'default'),
+        ('dark_theme', 'stata-dark'),
+    ])
+
     default_config = OrderedDict([('compiler', default_compiler_config),
-                                  ('cache', default_cache_config)])
+                                  ('cache', default_cache_config),
+                                  ('highlight_style', default_highlight_style)])
 
     config_path, config_exists = get_configuration_file_path()
     config = default_config.copy()
@@ -219,6 +225,10 @@ def get_cache_config():
     return _config['cache']
 
 
+def get_highlight_style_config():
+    return _config['highlight_style']
+
+
 def add_or_change_compiler_flags(flags):
     if not isinstance(flags, list) and not isinstance(flags, tuple):
         flags = [flags]