update readme

Author: hrj

README.md

@@ -1,2 +1,9 @@
 # treeChecker
 Check a direc-tree of files for red flags using OpenAI API compatible service
+
+It is a simple program that iterates recursively through a directory hierarchy and analyses each file (if its name matches
+the provided regex), by passing its contents along with the prompt to an LLM.
+
+See sample.sh for an example of how to invoke this.
+
+Note: You will need to either download treeChecker.jar from the releases, or build the project with IntelliJ.