Switch colors to chalk - Fixes #57

[fbartho]

This PR migrates prettyjson from colors to chalk - Related: #57 #54

This breaks support for the following "colors":

• rainbow
• zebra
• america
• trap
• random
• zalgo

These were present in colors.js and are not present in chalk

One of these "colors" (rainbow) is referenced in a unit test. Options:
A. Delete the unit test
B. Implement this color (and other alternative colors?) on top of chalk.js

Additionally, in chalk 5.x, they have gone ESM-only, so I pinned us to chalk @ 4.x -- chalk's 5.0 release links to Pure ESM

Features

• Hex Color Support! "#FFFFFF"
• options.unknownColorHandler by default warns users if a color isn't supported. This warning can be disabled via "ignore", or the user can provide a custom function to render a given input into the expected "color"
• Allow overriding of true/false color via options.trueColor, options.falseColor
• Allow overriding of null/undefined color via options.nullUndefinedColor

Remaining Tasks

• Resolve the broken test / alternative-colors decision
• Acknowledge chalk < 5 constraint, or decide how to proceed

[fbartho]

npm versions higher than 6 (which is what comes with node 14) change the version of package-lock.json from 1 to 2.

Version 2 is backwards compatible with package-lock.json version 1, but I didn't want to make that change in this PR.