Java 8 compatibility

[carlosame]

EchoSVG provides classes that are compatible with Java 8, however the Mozilla Rhino dependency requires Java 11 or later. If one attempts to build EchoSVG with Rhino 1.8.0 the following happens:

FAILURE: Build failed with an exception.

* What went wrong:
Execution failed for task ':echosvg-test-scripts:compileLegacyJava'.
> Could not resolve all files for configuration ':echosvg-test-scripts:compileClasspath'.
   > Could not resolve org.mozilla:rhino:1.8.0.
     Required by:
         project :echosvg-test-scripts > project :echosvg-bridge > project :echosvg-script
      > Dependency resolution is looking for a library compatible with JVM runtime version 8, but 'org.mozilla:rhino:1.8.0' is only compatible with JVM runtime version 11 or newer.

Moreover, apparently a lot of places have migrated from Java 8 to 11 or later during the previous year.

So the question is whether anyone is actually using EchoSVG on Java 8. If that is the case, please comment here. I'm also opening a poll about this (#120).