Add Unity 2020+ support

Author: TriceHelix

package.json

@@ -3,7 +3,7 @@
     "version": "1.0.0",
     "displayName": "Generic Burst Jobs",
     "description": "Support for generic, Burst compiled Job structs through automatic code analysis and generation",
-    "unity": "2022.3",
+    "unity": "2020.3",
     "documentationUrl": "https://github.com/TriceHelix/GenericBurstJobs",
     "changelogUrl": "https://github.com/TriceHelix/GenericBurstJobs",
     "license": "LICENSE.txt",