Checklist toolbar improvements

The previous version of the formatting toolbar was quite limited (intentional for MVP). In the latest version, I've extended and improved the options.

Here's the full list of ways to format your content

• List Item (A Checklist item)

• Header size 1 (H1)

• Header size 2 (H2)

• Header size 3 (H3)

• Paragraph

• Link (Will always open in a new tab)

• Bold

• Italic

• Underline

This feature change provides you with many ways to customize your checklists.