PHP 8 compatibility

See: https://jqueryui.com/autocomplete/#multiple

https://developer.mozilla.org/en-US/docs/Web/HTML/Element/label#using_the_for_attribute

We will change the date format in one go later.

system/htmly.php
- Loads language files from folder lang/
- Sets language settings for date and time format
system/includes/dispatch.php
- function i18n() returns translated strings

Without the step modifier users on Chrome mobile couldn't edit
blogs because the seconds were missing
(hh:mm while hh:mm:ss was expected)

This is my first commit, hope it worked :)

The ported version of Twenty Fifteen and Twenty Sixteen include with the
package. Maintenance and bugs fixes.

Simplify add and edit content. Bugs fixes and improvements.

Use URLify, add pager number, new variable etc.

Prepare release, improvements, and bugs fix  #226

Add new config: static.frontpage = "true" to enable the static
frontpage.

Use the pagedown extra instead of standard pagedown. Adding
sitemap.category.xml

Add category feature to the core.

Updated robots.txt + new htaccess files.

I made the following changes for the robots.txt and .htaccess files.

# robots.txt updated
- Allow theme assets (CSS, JS, Images, Fonts) for SEO
- Allow folder with uploaded images (/content/images)

# .httaccess files added
- /content - Deny all
- /content/images - Allow only jpg|png|gif
- /cache - Deny all
- /system - Deny all
- /system/admin/editor - Allow all
- /system/resources - Allow all
- /themes - Deny all
- /themes/blog/css - Allow all
- /themes/blog/fonts - Allow all
- /themes/blog/images - Allow all
- /themes/blog/js - Allow all
- /themes/clean/css - Allow all
- /themes/default/css  - Allow all
- /themes\default\img - Allow all
- /themes\logs\css - Allow all

Before this pull request, the 404 and 404-search templates where handled
as full HTML pages without the page context (layout).

With this pull request both pages are rendered inside the selected
themes layout. Additionally the 404 template now contains the "search
form" and the homepage link.

All Themes are already updated with the above changes.

This reverts commit 9fa8fab864.

Before this pull request, the 404 and 404-search templates where handled
as full HTML pages without the page context (layout).

With this pull request both pages are rendered inside the selected
themes layout. Additionally the 404 template now contains the "search
form" and the homepage link.

All Themes are already updated with the above changes.

Make the tag URL always lowercase and accept case insensitive URL e.g
/tag/htmly or /tag/HTMLy.