Add example with input variables

[idkjs]

No description provided.

[jeddeloh]

Thanks for the contribution! I haven't been able to look at this yet, but a couple things before I do:

1. Could you look at the package.json changes and confirm everything there is intentional?
2. Could you remove the yarn.lock files, I thought I'd added that to .gitignore, but I guess not
3. I would have expected the current mutation examples to include variables. Do they really not? If they do use variables, what are these examples showing that they do not?

Thanks, again! I'll try and get to this soon.

[jfrolich]

It looks like you a git reconciliation issue. You probably started this PR on a very old version of the the library and something went wrong while trying to merge the new changes.

I suggest to always look at the diff before you commit ;)