Allow to specify tab size

[timvahlbrock]

Is your feature request related to a problem? Please describe.
I switched to using tabs for indentation for accessibility reasons. In editors one can usually specify how much space a tab indentation corresponds. However, I haven't found such an option in carbon.

Describe the solution you'd like
An option to configure how much spaces a tab corresponds to.

Describe alternatives you've considered

• Converting the code to space based indentation, which somewhat annoying (although it can be performed automatically by running the prettier option)
• Sticking with default tab indentation.

Additional context
n/a

[timvahlbrock]

Tabs are also not visualized by carbon.