docs: add index.php/spark changes in changelog

[kenjis]

Description

• add index.php/spark changes in changelog
• fix ImportError on GitHub Actions. See https://github.com/codeigniter4/CodeIgniter4/runs/5714296426?check_suite_focus=true

  • ImportError: cannot import name 'environmentfilter' from 'jinja2' (/usr/local/lib/python3.10/site-packages/jinja2/init.py)
    make: *** [Makefile:20: html] Error 1

Checklist:

• Securely signed commits
• [] Component(s) with PHPDoc blocks, only if necessary or adds value
• [] Unit testing, with >80% coverage
• User guide updated
• [] Conforms to style guide

[samsonasik]

Thank you @kenjis

[MGatner]

👌