degrading maven compiler plugin to 3.12.1 as of jitpack not supportin…

…g maven above 3.6.3

pom.xml

@@ -19,7 +19,7 @@
             <plugin>
                 <groupId>org.apache.maven.plugins</groupId>
                 <artifactId>maven-compiler-plugin</artifactId>
-                <version>3.13.0</version>
+                <version>3.12.1</version>
                 <configuration>
                     <source>${maven.compiler.source}</source>
                     <target>${maven.compiler.target}</target>