[annotations] Add a README with a build instruction for maven

Summary:
Although, we have Makefile and BUCK build def, this is a maven project
which is supposed to be released to Maven Central, so it's worth
having a short instruction on how to build it with maven.

Reviewed By: mityal

Differential Revision: D18037109

fbshipit-source-id: 6aebf4384

infer/annotations/README.md

@@ -0,0 +1,14 @@
+# Infer annotations
+
+This project provides extra annotations for Java checkers, such as starvation or nullsafe.
+
+## How to build JARs (suitable for release)
+
+Make sure you have maven installed. `infer-annotaions` is a regular
+maven project, so regular maven commands apply. The following commands might be of interest:
+
+1. Build artifact jar (the one with class files): `mvn package`.
+2. Build sources jar: `mvn source:jar`
+3. Clean: mvn clean
+
+The resulting artifacts will be under `target/` folder.