Fix FontConfig after upgrade to new ImGui version. (#16)

Author: OndraVoves

src/gui.zig

@@ -175,17 +175,17 @@ pub const FontConfig = extern struct {
     font_data: ?*anyopaque,
     font_data_size: c_int,
     font_data_owned_by_atlas: bool,
+    merge_mode: bool,
+    pixel_snap_h: bool,
     font_no: c_int,
-    size_pixels: f32,
     oversample_h: c_int,
     oversample_v: c_int,
-    pixel_snap_h: bool,
+    size_pixels: f32,
     glyph_extra_spacing: [2]f32,
     glyph_offset: [2]f32,
     glyph_ranges: [*c]u16,
     glyph_min_advance_x: f32,
     glyph_max_advance_x: f32,
-    merge_mode: bool,
     font_builder_flags: FontBuilderFlags,
     rasterizer_multiply: f32,
     rasterizer_density: f32,