initial README.md file

Author: msailes

README.md

@@ -1,2 +1,36 @@
 # lambda-java17-layer
 AWS Lambda layer to enable Java 17 support
+
+## Usage
+
+- Create a function using the PROVIDED_AL2 runtime.
+- Add this layer to your function.
+
+## Java 17 
+
+A custom JRE is created to reduce final file size. Lambda has a 250MB unzipped file size limit.
+
+[Dockerfile](Dockerfile) describes how the JRE is built
+
+## JVM Settings
+
+The following JVM settings are added by default.
+
+```
+--add-opens java.base/java.util=ALL-UNNAMED 
+-XX:+TieredCompilation -XX:TieredStopAtLevel=1 
+-Xshare:on
+```
+
+Further suggestions welcomed
+
+## Java Class Path
+
+```
+aws-lambda-java-runtime-interface-client-1.1.0.jar
+aws-lambda-java-core-1.2.1.jar
+aws-lambda-java-serialization-1.0.0.jar
+$LAMBDA_TASK_ROOT
+$LAMBDA_TASK_ROOT/*
+$LAMBDA_TASK_ROOT/lib/*
+```