Function blender_armature::get_surrounding_keyframes

pub fn get_surrounding_keyframes(
    keyframes: &Vec<BoneKeyframe>, 
    current_frame: f32
) -> (BoneKeyframe, BoneKeyframe)

If you’re sampling frame 1.5 and there are three keyframes - 0, 2, 3 the surrounding keyframes are 0 and 2.

If you’re sampling frame 1.5 and there are three keyframes - 10, 15, 31 the surrounding keyframes are 0 and 0.

If you’re sampling frame 1.5 and there are three keyframes - 0, and 1 then the surrounding keyframes are 1 and 1.

We assume that the keyframes are stored in ascending order.

TODO: Binary search instead of linear