Update ReadMe.md to include build and publishing instructions

Author: flemming-n-larsen

ReadMe.md

@@ -3,4 +3,35 @@
 Codesize is a tool for calculating the bytecode size of a Java class file, ZIP/JAR archive.
 It is being used by Robocode to calculate the code size of robots after having compiled these.
 
-Read more about the [Code Size](https://robowiki.net/wiki/Code_Size) on the RoboWiki.
+Read more about the [Code Size](https://robowiki.net/wiki/Code_Size) on the RoboWiki.
+
+## Build
+
+To build Codesize, use Gradle:
+
+```sh
+./gradlew build
+```
+
+This will compile the project and create the JAR file in the `build/libs` directory.
+
+## Publishing
+
+Codesize uses in-memory PGP signing for publishing to OSSRH (Maven Central). You must provide the following properties
+in your `gradle.properties`:
+
+```
+signing.keyId=YOUR_KEY_ID
+signingKey=YOUR_ASCII_ARMOR_PRIVATE_KEY
+signingPassword=YOUR_KEY_PASSWORD
+ossrhUsername=YOUR_OSSRH_USERNAME
+ossrhPassword=YOUR_OSSRH_PASSWORD
+```
+
+To publish the artifact:
+
+```sh
+ ./gradlew publishToSonatype closeAndReleaseSonatypeStagingRepository
+```
+
+This will sign and upload the artifacts to the configured OSSRH repository.