Fix \uXXXX codes in composer.json

[upyx]

It fixes #1

Description

It adds a twig escaper for json based on json_encode instead of standard twig js encoder. So a new dependency "ext-json" was added.

Motivation and Context

To fix #1. Because it was really annoying.

How Has This Been Tested?

Unit tests pass. I've created a new project and checked it.

Types of changes

• 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)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• All new and existing tests passed.
• I have run composer run test locally, and there were no failures or errors.

[ramsey]

Thank you for contributing! 🎉