Add more tests to resistor-color

I think resistor-color on the WebAssembly track could benefit from more extensive tests as compared to the same exercise on other tracks. This is because the language lacks any string/array comparing methods that are present in higher level languages so some solutions may fail around edge cases.
This post is motivated by a few community solutions that take advantage of loading 4 bytes at a time to only compare a prefix of the input. These approaches may fail to disambiguate between “green” and “grey” when looking only at the first 3 characters or may fail on the input “red” when loading 4 characters.

I suggest we test all 10 colors, or at least add tests for “red” and “grey”.

Note, Suggesting Exercise Improvements | Exercism's Docs

Some of those points may not apply here, but the problem spec part likely does.

The resistor-color-duo test cases cover all 10 colors. We should implement the exercise.