Open UPM support

[hsandt]

Hello, I found that your package has an OpenUPM entry:

https://openupm.com/packages/com.ecasillas.missingrefsfinder/

but considering that README doesn't mention it, that it was "discovered" by someone else, and that it is marked "package not found" and even says:

No valid Git tag (opens new window) detected. Please contact the package owner to create at least one valid Git tag.

I can assume that this is not official support (and in fact, openupm add com.ecasillas.missingrefsfinder will fail).

Are you interested in supporting openupm?

The main benefit for my team is easy install without adding repo via git+ URL / editing Packages/manifest.json manually with git URL (which requires all team members to install standalone Git on their computer; of course they have some Git to clone the repo, but artists often use the one embedded in their Git clients).

Fortunately, this repo has no dependency so I can at least make it a submodule if needed.