Add letter-spacing edit option to TextEditor
Added missing letter-spacing to SvgTextEditor
(Tell us how to test the changes you made.)
- I confirmed this builds.
- I confirmed Krita ran and the relevant functions work.
-  I tested the relevant unit tests and can confirm they are not broken. (If not possible, don't hesitate to ask for help!) (macOS fails all text tests,it never finds the chosen font)
- I made sure my commits build individually and have good descriptions as per KDE guidelines.
- I made sure my code conforms to the standards set in the HACKING file.
- I can confirm the code is licensed and attributed appropriately, and that unattributed code is mine, as per KDE Licensing Policy.