chore: Adding composer package setup to workflow

[colinmurphy]

Description

What does this do

1. Fixed a typo in the plugin npm script package name (Copilot PR chore: Run version script when creating a release branch #311 )
2. Added a check and ran this script before committing the release branch (Copilot chore: Run version script when creating a release branch #311)
3. Added a valid package.json file for composer installs as plugin/package.json
4. Tested npm run version and updated the previews plugin (from 0.0.4 to the current version 0.0.5)
5. Tested adding this version to the new plugins/package.json .github/scripts/update_composer_package.sh "0.0.5" "https://github.com/wpengine/hwptoolkit/releases/download/%40wpengine%2Fhwp-previews-wordpress-plugin-0.0.5/hwp-previews.zip" "wpengine/previews" "A WordPress plugin for headless previews."
6. Updated release branch workflow to run this script
7. Renamed get-plugin-slug.sh to get_plugin_slug.sh

[!NOTE}
I will create a follow on PR (assuming this works) with docs for plugins (how to create them, add code quality, composer etc), How to install a plugin with composer.

Related Issue

#303

Dependant PRs

Type of Change

• ✅ Bug fix (non-breaking change which fixes an issue)
• ✨ New feature (non-breaking change which adds functionality)
• 💥 Breaking change (fix or feature that would cause existing functionality to change)
• 🧹 Code refactoring (no functional changes)
• 📄 Example update (no functional changes)
• 📝 Documentation update
• 🔍 Performance improvement
• 🧪 Test update

How Has This Been Tested?

Screenshots

Checklist

• I have read the CONTRIBUTING document
• My code follows the project's coding standards
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation (if applicable)
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works (if applicable)
• Any dependent changes have been highlighted, merged or published

[changeset-bot]

🦋 Changeset detected

Latest commit: 19b64ba

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

This PR includes changesets to release 1 package

Name	Type
@wpengine/hwp-previews-wordpress-plugin	Patch

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[github-actions]

ℹ️ Download the latest hwp-previews plugin zip from this PR
(See the 'Artifacts' section at the bottom)