feat: create optimized & resized images upon upload

- resize uploaded image to thumbnail, medium, large, feed, and id3 formats
- set image url formats where adapted in views
- set format sizes and extensions in Images config file for customization
- add validation for image uploads: `min_dims` and `is_image_squared`
- update codeigniter4 and myth-auth php packages to latest develop versions
- update npm packages to latest versions
- update public/.htaccess

closes #6