Support for `versionStrategy` conformance

[hamlim]

TL;DR:

• versionStrategy added to the config file - optional
  • Allowed values: 'pin' and 'loose'
    • 'loose' is the default if not provided
      • Allows any kind of versioning strategy within dependencies across the monorepo, e.g. caret ranges ^5 etc...
    • 'pin' enforces that all dependencies must specify complete versions

Implementation:

Could technically pull in a semver matching package from somewhere, but we might be able to get around a more naive implementation, specifically checking if the dep isn't:

• workspace:
• link:
• git:

(I think that's all of the supported special prefixes)

Otherwise, check if it doesn't begin with:

• ^
• ~

.... hmm ok as I'm reading these specs more and more I think it might be worth pulling in some kind of dependency for this: https://docs.npmjs.com/cli/v6/using-npm/semver#advanced-range-syntax

Why:

I recommend using the 'pin' strategy - it ensures that you have consistent versions especially when some tools ignore lock files. It also makes dependency upgrades specific instead of unknown (without inspecting the lockfile).

[hamlim]

Added support in v0.2.0