chore: Upgrade from yarn classic (v1.22) to pnpm v10

[bantic]

Upgrades from yarn classic as a package-manager to pnpm.

Followed guidance from https://dev.to/andreychernykh/yarn-npm-to-pnpm-migration-guide-2n04 and https://pnpm.io/installation.

In some cases I referred to existing v2 addons w/ pnpm (like ember-page-title) as a reference.
Also looked at https://github.com/embroider-build/addon-blueprint.

pnpm surfaced some mistakes where dependencies hadn't been correctly defined (but were hoisted when using yarn classic). It also complains more loudly about deprecated deps which led me to upgrade eslint 8 to 9 for addon/.

This PR diverges a little from the github workflow guidance from pnpm (https://pnpm.io/continuous-integration#github-actions) in that it uses volta's cli action instead of setup-node.

This change sets up this repo so that:

• locally:
  • node version is managed by volta (via the top-level volta.node in package.json)
  • pnpm version is managed by corepack (via top-level packageManager in package.json)
• at CI:
  • volta-cli action used, which reads volta.node from package.json and sets up node
  • setup-pnpm action used, which reads packageManager from package.json and sets up pnpm

This uses actions/cache directly, and adds an extra step to each job to find the pnpm "store" path to use for the cache. I determined how to do this by looking at how setup-node does it when cache: 'pnpm' is used (https://github.com/actions/setup-node/blob/48b90677b6048efbc723b11a94acb950d3f1ac36/src/cache-utils.ts#L30-L38), and found some examples in the wild like: https://gist.github.com/belgattitude/838b2eba30c324f1f0033a797bab2e31.

Other changes:

• add the prettier plugin for ember-template-lint (and fix the surfaced prettier lint errors in addon hbs files)
• update contributer.md to fix update contributor docs to reflect v2 addon format #67

[bantic]

This is the pnpm way to refer to a workspace package, see https://pnpm.io/workspaces#workspace-protocol-workspace

[bantic]

Added to upgrade eslint 8 to 9 for the addon/ dir, copied with minor changes from test-app's eslint config

[bantic]

Renamed to .mjs to remove a deprecation warning from rollup.

The other changes are cosmetic, applied by prettier to fix linting.

[bantic]

pnpm-maintained package, suggested by https://dev.to/andreychernykh/yarn-npm-to-pnpm-migration-guide-2n04

[bantic]

Dropped this because we don't want it to be included when doing pnpm test.
We run the scenarios individually in the workflow

[bantic]

pnpm identified that these had been missing before (yarn classic had been hoisting them from elsewhere which made them available to the test-app. pnpm doesn't allow that, so they have to be explicitly added)

[bantic]

Verified that the cache is working correctly by reviewing a recent run:

[eliasdawson-addepar]

Is there a reason you prefer to use volta to manage pnpm version? @yanglinz's recommendation was to use corepack for pnpm management and only use Volta for node version.

[bantic]

Is there a reason you prefer to use volta to manage pnpm version?

I misunderstood that. I'll retool this once again to use volta only for node and use corepack for pnpm.

[mixonic]

I think this is on the right track now. Deferring to @yanglinz for alignment on the right timing to introduce corepack into an Addepar repo. I would doubt most people have it configured today, but with your approval that doesn't need to prevent us from starting to use it inside Web Core (likely the only people who will touch this code in the next few months).

[bantic]

This sets up node, using the node version from package.json#volta.node

[bantic]

This sets up pnpm, using the pnpm version from package.json#packageManager