* feat(font): add font placeholder drawing configuration * Turn on placeholder by default in Kconfig Signed-off-by: pengyiqiang <pengyiqiang@xiaomi.com> * When disabled LV_USE_FONT_PLACEHOLDER set box_w=0 * Remove placeholder_font to get glyphs Signed-off-by: pengyiqiang <pengyiqiang@xiaomi.com> Co-authored-by: pengyiqiang <pengyiqiang@xiaomi.com>