examples: use fontstash wrapper calls (#12718)

vlib/sokol/sfons/sfons.c.v

@@ -6,12 +6,12 @@ import fontstash
 const used_import = fontstash.used_import + 1
 
 [inline]
-pub fn create(width int, height int, flags int) &C.FONScontext {
+pub fn create(width int, height int, flags int) &fontstash.Context {
 	return C.sfons_create(width, height, flags)
 }
 
 [inline]
-pub fn destroy(ctx &C.FONScontext) {
+pub fn destroy(ctx &fontstash.Context) {
 	C.sfons_destroy(ctx)
 }
 
@@ -21,6 +21,6 @@ pub fn rgba(r byte, g byte, b byte, a byte) u32 {
 }
 
 [inline]
-pub fn flush(ctx &C.FONScontext) {
+pub fn flush(ctx &fontstash.Context) {
 	C.sfons_flush(ctx)
 }