feat: Add ansi option to mark ANSI extra as required or not

This helps decide whether to include the ANSI CSS file into the final site.

Issue #28: #28
Issue #29: #29

mkdocs.yml

@@ -120,7 +120,8 @@ markdown_extensions:
 
 plugins:
 - search
-- markdown-exec
+- markdown-exec:
+    ansi: required
 - gen-files:
     scripts:
     - scripts/gen_ref_nav.py

src/markdown_exec/mkdocs_plugin.py

@@ -49,6 +49,8 @@ def _get_logger(name: str) -> _LoggerAdapter:
 class MarkdownExecPluginConfig(Config):
     """Configuration of the plugin (for `mkdocs.yml`)."""
 
+    ansi: str | bool = config_options.Choice(("auto", "off", "required", True, False), default="auto")
+    """Whether the `ansi` extra is required when installing the package."""
     languages: list[str] = config_options.ListOfItems(config_options.Choice(formatters.keys()), default=list(formatters.keys()))
     """Which languages to enabled the extension for."""
 
@@ -96,7 +98,8 @@ def on_env(  # noqa: D102
         config: MkDocsConfig,
         files: Files,  # noqa: ARG002
     ) -> Environment | None:
-        self._add_css(config, "ansi.css")
+        if self.config.ansi in ("required", True) or (self.config.ansi == "auto" and ansi_ok):
+            self._add_css(config, "ansi.css")
         if "pyodide" in self.languages:
             self._add_css(config, "pyodide.css")
             self._add_js(config, "pyodide.js")