add yarn workspaces

[jroebu14]

Resolves #4332

Overall change:
Adds Yarn Workspaces.

Update
Talos depends on Lerna exec so not cannot be removed unless we find a replacement for either Lerna or Talos.

Code changes:

• Removes each package's lockfile. Yarn Workspaces uses a single lockfile rather than one for each workspace
• Removes ci:packages script:
  • What it did: installed dependencies in each package
  • Why is it removed: because Yarn installs all package's dependencies in a single pass in the root node_modules
• Removes install:packages script:
  • What it did: installed all package's dependencies and linked any cross-dependencies
  • Why is it removed: because yarn install installs all package's dependencies in a single pass in the root node_modules and links cross-dependencies by default
• Replaces lerna exec with yarn workspaces run
  • What it did: runs commands in each package - we use it for building packages with babel
  • Why is it replaced: yarn workspaces run is native to Yarn and does the same thing as lerna exec
• Changes psammead moment-timezone-include package to use commonjs modules. This is because the postinstall script in this package's package.json (which runs a node script in the build directory) ran before the postinstall script in the root package.json (which transpiles code and generates the build directories) and attempts to run a script that doesn't yet exist. Using commonjs modules means we don't need to transpile the code before running the node script.
• Updates the changeScanner script to check that the root yarn.lock has been updated if any package's dependencies have been updated

---

• I have assigned myself to this PR and the corresponding issues
• Automated jest tests added (for new features) or updated (for existing features)
• This PR requires manual testing

[github-actions]

Checkout your storybook preview here http://psammead-preview.tools.bbc.co.uk/4368

[chris-hinds]

Nice work Jonathan. Does this still allow us to publish packages publicly individually to NPM as we do now. I thought the impression that by default yarn wanted packages to be private?

[jroebu14]

I thought it was just the root package that had to be private

[chris-hinds]

I thought it was just the root package that had to be private

You are right, just read up on it again.

[andrewscfc]

LGTM, really excited to see if this facilitates cross repo dev 🤞 Just a few questions around the change scanner but not blocking

[chris-hinds]

Changes look great. Thanks for this @jroebu14