Change the default value of `terminal.allowCommands` from an empty array to `['ls', 'echo']`. This change prevents users from running all available commands by default in tutorials, enhancing security and focus. Lesson authors can still allow all commands by specifying `terminal.allowCommands: []` in the metadata.

BREAKING CHANGE: The default value of `terminal.allowCommands` is now restricted to `['ls', 'echo']`. To allow all commands, explicitly set `terminal.allowCommands: []` in the metadata.

Closes #302

adjust tests to expect ['ls', 'echo'] as default allowCommands when undefined, aligning tests with updated functionality

closes #302

Co-authored-by: Ari Perkkiö <ari.perkkio@gmail.com>

Co-authored-by: Ari Perkkiö <ari.perkkio@gmail.com>

Change the default value of `terminal.allowCommands` from an empty array to `['ls', 'echo']`. This update enhances security and focus by limiting the commands available in tutorials by default.

Lesson authors can still enable all commands by setting `terminal.allowCommands: []` explicitly in the metadata.

BREAKING CHANGE: The default value of `terminal.allowCommands` is now restricted to `['ls', 'echo']`. To allow all commands, explicitly set `terminal.allowCommands: []` in the metadata.

Closes #372