Offsets for rectangles, borders, etc.
Used all over the place by GUIStyle.
| bottom | Bottom edge size. |
| horizontal | Shortcut for left + right. (Read Only) |
| left | Left edge size. |
| right | Right edge size. |
| top | Top edge size. |
| vertical | Shortcut for top + bottom. (Read Only) |
| RectOffset | Creates a new rectangle with offsets. |