#5 Issue: Readme.md updated

[aliiakbarkhan]

Key changes I have made:

1. Java version: Change from Java 8 to Java 11 (matching build.gradle which sets JavaVersion.VERSION_11)
2. Source placement: Clarify the Gradle standard layout (src/main/java for main sources, src/test/java for test sources, src/main/java/example for example files — excluded from the main jar)
3. Build output: The javac command for compiling OTF sources should use semicolons on Windows (path separator)
4. Step numbering: Fix the duplicate step number (there are two step 5s)
5. jpf-core compatibility: Note that jpf-core should also be built with Java 11