oppia: It is not possible to search by pressing the Enter key on the classroom page search bar

Describe the bug It is not possible to search for lessons by pressing the enter key on the search bar on the classroom page.

To Reproduce Steps to reproduce the behavior:

1. Go to the classroom page on the test server.
2. Type something in the search bar which appears towards the bottom of the page
3. Press ‘Enter’ on the keyboard
4. Notice that the search is not started unless you ‘click’ on the search icon.

Observed behavior Pressing the enter key doesn’t start the search.

Expected behavior Pressing the enter key should start the search.

Possible steps to fix the issue

1. Make sure you are able to run the Oppia dev server.
2. Navigate to core/templates/pages/library-page/search-bar/search-bar.component.html and add an event to detect when the enter key is pressed.
3. Program that event to trigger the search function when it detects the pressing of the enter key.