feat: Added support for horizontal flip sourceTexture

[MaximKurbanov]

When I added support for "VUZIX M400 SMART GLASSES" to the project, the picture from the glasses was diagonally flipped. So I added the horizontal and diagonal flip.

videoStreamTrack = new VideoStreamTrack(webCamTexture, false, true); //Flip horizontaly
sourceRawImage.uvRect = new Rect(1, 1, -1, -1); //Flip diagonally for display

[karasusan]

@MaximKurbanov

I couldn't imagine the usage what you want when I designed this constructor. This PR makes sense to me but I want to create a new constructor instead of this.

public VideoStreamTrack(Texture texture, Vector2 scale, Vector2 offset) 

[MaximKurbanov]

Old:

videoStreamTrack = new VideoStreamTrack(webCamTexture, false, true); //Flip horizontaly
sourceRawImage.uvRect = new Rect(1, 1, -1, -1); //Flip diagonally for display

Now:

videoStreamTrack = new VideoStreamTrack(webCamTexture, CopyTextureHelper.DiagonalFlipCopy);
sourceImage.uvRect = new Rect(1, 1, -1, -1); //Flip diagonally for display

[karasusan]

@MaximKurbanov It looks good to me.