Allow user to add a new notebook

[Abijeet]

I should be able to add a new notebook and see it in the list of notebooks. When I select that notebook, the notebook should be displayed in the tab, with it's notes listed inside.

Related to #1

[Abijeet]

TODO

• Auto close the dialog after adding the Notebook
• When the dialog opens focus on the textbox.

[Abijeet]

Opened #31 to track these issues.