add configuration section with local workerd linking to Miniflare readme

[dario-piotrowicz]

This PR is simply adding info about the MINIFLARE_WORKERD_PATH env variable in the main Miniflare readme
(each time I need to use the env variable I need to dig through the code for it etc... I figured it could be worth to properly document this?)

Author has addressed the following

• Tests
  • TODO (before merge)
  • Included
  • Not necessary because: this is a simple md change
• E2E Tests CI Job required? (Use "e2e" label or ask maintainer to run separately)
  • I don't know
  • Required / Maybe required
  • Not required because: this is a simple md change
• Changeset (Changeset guidelines)
  • TODO (before merge)
  • Included (maybe it shouldn't be... 🤷 I'm totally happy with removing it if it's incorrect here)
  • Not necessary because:
• Public documentation
  • TODO (before merge)
  • Cloudflare docs PR(s): https://github.com/cloudflare/cloudflare-docs/pull/...
  • Not necessary because: this is a simple md change

[changeset-bot]

🦋 Changeset detected

Latest commit: 71baeb1

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 4 packages

Name	Type
miniflare	Patch
@cloudflare/pages-shared	Patch
@cloudflare/vitest-pool-workers	Patch
wrangler	Patch

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[github-actions]

A wrangler prerelease is available for testing. You can install this latest build in your project with:

npm install --save-dev https://prerelease-registry.devprod.cloudflare.dev/workers-sdk/runs/9244105747/npm-package-wrangler-5921

You can reference the automatically updated head of this PR with:

npm install --save-dev https://prerelease-registry.devprod.cloudflare.dev/workers-sdk/prs/5921/npm-package-wrangler-5921

Or you can use npx with this latest build directly:

npx https://prerelease-registry.devprod.cloudflare.dev/workers-sdk/runs/9244105747/npm-package-wrangler-5921 dev path/to/script.js

Additional artifacts:

npx https://prerelease-registry.devprod.cloudflare.dev/workers-sdk/runs/9244105747/npm-package-create-cloudflare-5921 --no-auto-update

npm install https://prerelease-registry.devprod.cloudflare.dev/workers-sdk/runs/9244105747/npm-package-cloudflare-kv-asset-handler-5921

npm install https://prerelease-registry.devprod.cloudflare.dev/workers-sdk/runs/9244105747/npm-package-miniflare-5921

npm install https://prerelease-registry.devprod.cloudflare.dev/workers-sdk/runs/9244105747/npm-package-cloudflare-pages-shared-5921

npm install https://prerelease-registry.devprod.cloudflare.dev/workers-sdk/runs/9244105747/npm-package-cloudflare-vitest-pool-workers-5921

Note that these links will no longer work once the GitHub Actions artifact expires.

---

wrangler@3.57.1 includes the following runtime dependencies:

Package	Constraint	Resolved
miniflare	workspace:*	3.20240512.0
workerd	1.20240512.0	1.20240512.0
workerd --version	1.20240512.0	2024-05-12

Please ensure constraints are pinned, and miniflare/workerd minor versions match.