New design added to megamenu items

[hsntareq]

This request contains several updates as follows:

• MegaMenu items adding modal is designed newly
• Options are now at the left side and always visible while editing
• Row & column can be added using provided sample layout and custom way. All width will based on percentage (%), maximum is 100%.
• Row add remove feature is added
• Column add-remove feature is added
• Column is now resizable by input or pressing +- button
• Moved the existing every action (ajax) change to save button
• Toast management is added for actions
• Widget search field is added from widget modal panel
• Widget can be added by the add button of any column
• For the block type theme a backend dynamic block is added