[jnigen] Updated docs to reflect renames (https://github.com/dart-lang/jnigen/issues/146)

* Updated docs to reflect renames (`JniObject` -> `JObject`)
* Updated llvm versions for linux dylib lookup as tests weren't passing
4 files changed
tree: 71f09773f988e3f89355166faec3db7c23e3e950
  1. .github/
  2. pkgs/