feat: add spa-loading-template.html to content config

[nikolasdas]

🔗 Linked issue

resolves #906

❓ Type of change

• [x] 📖 Documentation (updates to the documentation or readme)
• [ ] 🐞 Bug fix (a non-breaking change that fixes an issue)
• [x] 👌 Enhancement (improving an existing functionality)
• [ ] ✨ New feature (a non-breaking change that adds functionality)
• [ ] 🧹 Chore (updates to the build process or auxiliary tools and libraries)
• [ ] ⚠️ Breaking change (fix or feature that would cause existing functionality to change)

📚 Description

This simply adds spa-loading-template.html to the default content config and updates the docs accordingly

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[what-the-diff[bot]]

PR Summary

• Added a new template to the configuration The team included a new file named spa-loading-template.html within the content paths specified in our Tailwind configuration.

• Updated Resolver Logic The system used for fetching templates was updated. It will now include the newly added spa-loading-template.html.

These changes ensure that the new template can be easily identified and utilized by our system, improving the product's flexibility and usability.