Several changes have been made across multiple files to enhance code readability and follow safer
coding practices.

1. Breakdown of long lines of attributes/code into multiple lines with added comments for better
readability. This was done in Submenu.php

2. Replaced '==' operation with 'empty()' function to check for empty strings in Submenu.php

3. Safer checking of if method 'getCachePath' exists on 'getSite' to avoid potential errors &
Ensure the last insert ID is always an integer in the database PDO in DropDownMenu.php and
Factory.php

4. Refactor conditions for more clear type hinting in multiple files; including
Independent/Handler.php, Independent/Items/AbstractMenuItem.php, Independent/Items/Site.php,
Independent/Menu.php, MegaMenu.php, and NavTabs.php

The concept of safe concatenation or use of '|null|' has been introduced where needed across many
files.

Related: #38

New project setting to set the breakpoint to swtich to mobile menu.

Related: #34

refactor: Refactor name from MenuAdvanced to SlideOutAdvanced [SlideOutAdvanced] #23

refactor: Some design improvements (SlideOut)

fix: Berechnung der Breite von Nav abhängig von der Fensterbreite - sonst verschwindet der Button.