Use tabs for indentation in Markdown editor and align display to RTE and Markdown Viewer display

[laurent22]

The RTE and Markdown Viewer use the same indentation for lists for consistency. The Markdown editor however use spaces for indentation - not only it makes the indentation tiny but it means it also cannot be changed via CSS.

If possible we should instead use tabs for indentation which will make it possible to match the design of the viewer and RTE and will make list indentation more pronounced and stylable via CSS.

Additionally the space between bullet points is tiny on the Markdown editor, but that maybe need to be addressed in the Extra Settings plugin since it's related to the "Hide Markdown" mode.

Markdown viewer (and RTE):

Markdown editor:

Due to the tiny indentation level it's difficult to follow that kind of list at a glance. Even more so for checkbox lists because all bullet points will look the same.

[personalizedrefrigerator]

The RTE and Markdown Viewer use the same indentation for lists for consistency. The Markdown editor however use spaces for indentation - not only it makes the indentation tiny but it means it also cannot be changed via CSS.

For me, Joplin seems to use tabs for list indentation. For example,

- **Technology**
	- Computers
	- Laptops
		- MacBook
		- Dell XPS
	- Desktops
		- Gaming PCs
		- Workstations
	- Smartphones
		- iOS
		- Android

For comparison, I'm attaching my system version information:

Version information

Joplin 3.2.11 (prod, linux)

Client ID: 5d8cf789194849bda110c5647b766c5d
Sync Version: 3
Profile Version: 47
Keychain Supported: No

Revision: 2fba101

Backup: 1.4.2
Extra Markdown editor settings: 1.8.0
Freehand Drawing: 2.14.0
Menu Test: 1.0.0
RevealJS Integration: 0.15.0

I'm creating sub list items by pressing tab.

[laurent22]

Oh indeed it's using tab for me too. I copied and pasted that list from somewhere which is probably why it's indented with four tabs. Could we just increase the tab size a bit to make it match the one in the viewer? Looks like it's missing 5 pixels or so