Font Manager Improvements

I thought of a few items that would be beneficial when using the Font Manager especially when dealing with multiple languages.

  1. Add ability to set font fallback to both created fonts and built in LVGL fonts. The only way to do this currently in LVGL v8 due to the structure being constant is to modify the generated font file. This gets erased every time the files are export UI files from SDS. The fallback is nice when many multilanguage fonts don’t include symbols or may be missing certain language characters.

  2. Add ability to create a font from multiple font files like you can do with LVGL’s online font converter. Another way to solve this would be to add functionality to the online font converter to output a new merged font file for use in SDS.