Merge branch 'master' of https://github.com/UnityTechnologies/ShaderGraph_ExampleLibrary

# By andytouch
# Via GitHub
* 'master' of https://github.com/UnityTechnologies/ShaderGraph_ExampleLibrary:
  RM: Added Spiral Particle

README.md

 Particles:
 - Basic Solid Circle
 - Basic Soft Circle
+- Spiral