Make fonts const in lvgl format

As discussed here the lvgl fonts could be const with a few modifications.

@puzrin If you have some time could you modify the end of the generated fonts like this? See the parts added with #if LV_VERSION_CHECK(8, 0, 0).

/*--------------------
 *  ALL CUSTOM DATA
 *--------------------*/
#if LV_VERSION_CHECK(8, 0, 0)
/*Store all the custom data of the font*/
static  lv_font_fmt_txt_glyph_cache_t cache;
static const lv_font_fmt_txt_dsc_t font_dsc = {
#else
static lv_font_fmt_txt_dsc_t font_dsc = {
#endif
    .glyph_bitmap = gylph_bitmap,
    .glyph_dsc = glyph_dsc,
    .cmaps = cmaps,
    .kern_dsc = &kern_classes,
    .kern_scale = 16,
    .cmap_num = 2,
    .bpp = 4,
    .kern_classes = 1,
    .bitmap_format = 0,
#if LV_VERSION_CHECK(8, 0, 0)
    .cache = &cache
#endif
};

/*-----------------
 *  PUBLIC FONT
 *----------------*/

/*Initialize a public general font descriptor*/
#if LV_VERSION_CHECK(8, 0, 0)
const lv_font_t lv_font_montserrat_14 = {
#else
lv_font_t lv_font_montserrat_14 = {
#endif
    .get_glyph_dsc = lv_font_get_glyph_dsc_fmt_txt,    /*Function pointer to get glyph's data*/
    .get_glyph_bitmap = lv_font_get_bitmap_fmt_txt,    /*Function pointer to get glyph's bitmap*/
    .line_height = 16,          /*The maximum line height required by the font*/
    .base_line = 3,             /*Baseline measured from the bottom of the line*/
#if !(LVGL_VERSION_MAJOR == 6 && LVGL_VERSION_MINOR == 0)
    .subpx = LV_FONT_SUBPX_NONE,
#endif
#if LV_VERSION_CHECK(7, 4, 0)
    .underline_position = -1,
    .underline_thickness = 1,
#endif
    .dsc = &font_dsc           /*The custom font data. Will be accessed by `get_glyph_bitmap/dsc` */
};

[puzrin]

Released 1.5.0

[kisvegabor]

Works well, thank you!