feat: Add rgb decimal fraction, scientific notation support

[camdecoster]

Description

Updates rgb regex to handle decimal fractions, scientific notation.

Closes #77.

Changes

• Updates rgb regex
• Parses regex results as floats
• Adds tests per above changes

Testing

• Be on master
• Call the library with decimal fraction values: cs.get("rgb(1, 2.0, 3)")
• Call the library with scientific notation values: cs.get("rgb(1e2, 2.0E2, 3e2)")
• Note that a null value is returned for both calls
• Switch to this branch
• Call the library with decimal fraction values: cs.get("rgb(1, 2.0, 3)")
• Call the library with scientific notation values: cs.get("rgb(1e2, 2.0E2, 3e2)")
• Note that an array of numbers is returned with the proper values for both calls

[camdecoster]

Hello @Qix-! Do you have time to take a look at this PR and #81?

[Qix-]

Hi there, thanks! Might be a little bit before it's released unfortunately, and sorry it took so long to review - have had a very long four weeks and I'm currently sick.