FeatReq: use the Textual reccomended spec for the terminal fonts and line spacing and character spacing

According to the Textual FAQ the issues with the terminal characters can be solved by using the reccomended settings:
* FONT = Menlo
* STYLE = Regular
* Character Spacing = 1.0
* Line Spacing = 0.805

SOURCE: https://github.com/Textualize/textual/blob/main/docs/FAQ.md#why-doesnt-textual-look-good-on-macos

Unfortunately the config utility of a-Shell can only set the Font family, not Character Spacing or Line Spacing.
Is it possible to add those two settings?

HOW TO REPRODUCE THE BUG
Here is a zip file with two small python scripts you can use to test the characters issues on a-Shell:

[test_code_textual_characters_issues.zip](https://github.com/holzschu/a-shell/files/12481060/test_code_textual_characters_issues.zip)

Of course you also need to install the Textual package:

https://pypi.org/project/textual/