Add required 'operation' to inputs

[ben-v]

Added 'operation' type to inputs in order to more cleanly separate set field(s) and clear field(s) operations. Was trying to clear a single field by assigning an empty string to the 'values' input. But, the parsing of the values input (empty) string into an array would not work since it in effect was trying to interpret an empty string and the logical evaluation "if (inputs.values)" to see if setting/clearing field(s) would equate to false. By adding an operation to the inputs, explicitly state what the operation is, i.e. "get" values for the specified field(s), "set" the specified field(s) to the specified value(s) or "clear" the specified field(s).

[ben-v]

This is a great library! Hope you find my contribution helpful.

[EndBug]

Hi, thanks for opening this, this is great ✅

I'd normally leave a review with comments, but my changes are so trivial that I'll just merge the PR and push them later, just to save some time 😅

@all-contributors please add @ben-v for their code contributions

[EndBug]

My bad, let's try it again
@all-contributors please add @ben-v for their code contributions

[allcontributors]

@EndBug

I've put up a pull request to add @ben-v! 🎉

[ben-v]

Great!! Thank you! Again, this is a great library.

[EndBug]

@ben-v The changes have been published in v2.0.0 (also v2 and latest)
Thanks again for the PR ❤️