Improved Unity 2021 support

• Removed RenderEmulation class
• Replaced RTHandles with RenderTextures for Unity 2021 and lower
• Fixed device orientation bug with blur in Unity 2021 and lower

What's Changed

• Set RT wrapping mode to clamp by @Mohelm97 in #4

New Contributors

• @Mohelm97 made their first contribution in #4

Full Changelog: 0.1.2...0.2.0