Fix #81

Fails Store validation

> 3.2.g Any video documentation or tutorials should be uploaded online (Youtube, Vimeo, etc.) and not included in your projects. A link to your video should be mentioned in your written documentation.

Could be included in the Trial asset though.

Add links to other release notes of components vlc-unity uses.

this got lost somehow

it's now untracked in /Assets/PluginSource/sdk/**

Unity provides some resources on startup (unless it fails to initialize d3d11 properly).
We create a d3d11 device.
When the cleanup callback is called, we can release most of the resources but not our d3d11 device.
When the mediaplayer is released, we can unsub from the callbacks and release the d3d11 device we created.

this isn't optimal but if Unity fails to initialize properly like it does on some computers for some reason, the Editor will crash without this check.
getVideoFrame is called from the C# script in the Unity lifecycle Update() function which is called on each game frame.