fix: change the to_int_rect method

[Its-Just-Nans]

The to_int_rect uses an unwrap that can crash because the method from_xywh is converting i32 to u32

pub fn from_xywh(x: i32, y: i32, width: u32, height: u32) -> Option<Self> {                                                                                                         
    x.checked_add(i32::try_from(width).ok()?)?;                                                                                                                                     
    y.checked_add(i32::try_from(height).ok()?)?;

I think to_int_rect should return Option<IntSize>

Note:

• right now, this is a breaking change, but it can be a non-breaking change if we add a safe_to_int_rect method instead
• i32 range is -2_147_483_648i32 => 2_147_483_647i32
• u32 range is 0u32 => 4_294_967_295u32
• Related to Panic attempt to multiply with overflow in crates/resvg/src/lib.rs resvg#937

[Its-Just-Nans]

Also related to linebender/resvg#935

tiny-skia-path-0.12.0/src/size.rs:89:63:
called `Option::unwrap()` on a `None` value

  11:     0x61cb499bf669 - core[37f591cfbe66b0b1]::option::unwrap_failed
  12:     0x61cb4993f407 - <tiny_skia_path[6b23af959a23f32e]::size::IntSize>::to_int_rect
  13:     0x61cb496f37f6 - <tiny_skia[da2ae6e13adabe9d]::pixmap::PixmapMut>::fill_path
  14:     0x61cb49681423 - resvg[2ecdb20cebe6712c]::path::fill_path
  15:     0x61cb4967db93 - resvg[2ecdb20cebe6712c]::render::render_nodes