[WEB-434] feat: add support to insert a new empty line on clicking at bottom of the editor

[Palanikannan1437]

Description

This PR adds in support to add empty spaces wherever you weren't able to navigate into areas in a more intuitive way for all the below cases.

Tables

1. If table is at the end of the document -> You can navigate to ANY cell in the last row of the table and press down arrow key which will insert a new empty node at the bottom of the table and focus the cursor onto it.
2. If table is at the start of the document -> You can navigate to any cell in the first row of the table and press up arrow key which will insert a new empty node at the top of the table and focus the cursor onto it.

Images

1. If image is at the end of the document -> You can navigate to the image and press down arrow key which will insert a new empty node at the bottom of the image and focus the cursor onto it.
2. If image is at the start of the document -> You can navigate to the image and press up arrow key which will insert a new empty node at the top of the image and focus the cursor onto it.

In cases where you want to insert between nodes, you can either use the gap cursor that'll appear (example if image and table are consecutively placed) using your keyboard, or use the drag handles.

Added support to insert a new line at the bottom of the editor on clicking on the editor container.

Added support to automatically insert a new empty node at bottom of the table and image while navigating via down arrow in the table from any of the cells in the last row.