Add indent/Outdent toolbar options

**Is your feature request related to a problem? Please describe.**
Unable to easily create indented lists or text

**Describe the solution you'd like**
I'd love to see the addition of indent and outdent toolbar icons that enabled this functionality so that users that don't have markdown knowledge are able to acheive this.

**Describe alternatives you've considered**
Only alternative I can think of is switching to an alternative editor.

**Additional context**

- Indent would need to insert 2 spaces at the start of selected lines, or line where cursor is if no current selection
- Outdent would need to remove 2 empty spaces at start of selected lines (if there were any), or line where cursor is if no current selection