Add docs on global button text and overrides

Author: agriyakhetarpal

docs/configuration.md

@@ -67,6 +67,23 @@ jupyterlite_config = "jupyter_lite_config.json"
 jupyterlite_overrides = "overrides.json"
 ```
 
+# Setting default button texts for the `JupyterLite`, `NotebookLite`, and `Voici` directives
+
+When using the `:new_tab:` option in the `JupyterLite`, `NotebookLite`, and `Voici` directives,
+the button text defaults to "Open as a notebook" and "Open with Voici", respectively.
+
+You can optionally the button text on a global level for these directives by setting the
+following values in your `conf.py` file:
+
+```python
+jupyterlite_button_text = "My custom JupyterLite button text"
+notebooklite_button_text = "My custom NotebookLite button text"
+voici_button_text = "My custom Voici button text"
+```
+
+You can override this text on a per-directive basis by passing the `:button_text:` option
+to the directive. Note that this is compatible only if `:new_tab:` is also provided.
+
 ## Strip particular tagged cells from IPython Notebooks
 
 When using the `NotebookLite`, `JupyterLite`, or `Voici` directives with a notebook passed to them, you can