use a configuration option of type str instead

Author: keewis

jupyterlite_sphinx/jupyterlite_sphinx.py

@@ -820,13 +820,12 @@ def run(self):
 
         if notebook_unique_name is None:
             nb = examples_to_notebook(self.content, warning_text=warning_text)
-            preamble_path = Path("try_examples_preamble.py")
-            if preamble_path.is_file():
-                preamble = preamble_path.read_text()
-                # or raise an error if `preamble` is empty
-                if preamble:
-                    # insert after the "experimental" warning
-                    nb.cells.insert(1, new_code_cell(preamble))
+
+            preamble = self.env.config.try_examples_preamble
+            if preamble:
+                # insert after the "experimental" warning
+                nb.cells.insert(1, new_code_cell(preamble))
+
             self.content = None
             notebooks_dir = Path(self.env.app.srcdir) / CONTENT_DIR
             notebook_unique_name = f"{uuid4()}.ipynb".replace("-", "_")
@@ -1134,6 +1133,7 @@ def setup(app):
         default=None,
         rebuild="html",
     )
+    app.add_config_value("try_examples_preamble", default=None, rebuild="html")
 
     # Allow customising the button text for each directive (this is useful
     # only when "new_tab" is set to True)