Add 2.2.0 to compatibility matrix. (#30)

Author: justinkambic

README.md

@@ -71,6 +71,7 @@ are assigned likewise. For instance, increasing support from LibRaw version 0.19
 | 1.0.0               | 0.19.5         | 64, 67, 72, 79, 83, 88 |
 | 2.0.0               | 0.20.0         | 64, 67, 72, 79, 83, 88 |
 | 2.1.0               | 0.20.1         | 64, 67, 72, 79, 83, 88 |
+| 2.2.0               | 0.20.2         | 64, 67, 72, 79, 83, 88 |
 
 #### Node release version matrix