update root folder links

[Arhell]

Q	A
Is bugfix?	✔️/❌
New feature?	✔️/❌
Breaks BC?	✔️/❌

resolve https://github.com/yiisoft/yii-bootstrap5/issues/143

[what-the-diff[bot]]

PR Summary

• Enhanced URL Security
  • Updated several website links to use the more secure HTTPS protocol instead of the older, less secure HTTP. This ensures a more secure connection when accessing these websites and boosts user confidence in the security of our platform. Specific changes include:
  • The website link for Bootstrap, upgraded from http://getbootstrap.com/ to https://getbootstrap.com/
  • The website link for Yii Framework, upgraded from http://www.yiiframework.com/ to https://www.yiiframework.com/
  • The website link for Composer, upgraded from http://getcomposer.org/download/ to https://getcomposer.org/download/