fix: get the script by id instead of depending on document.currentScr…

[creativeindustriesgroup]

Refactor the current method for getting the current script to make it more reliable. Fixes #676.

Improvements to widget script handling:

• Updated the widget script identification logic to use document.getElementById('hievent-widget-script') instead of relying on document.currentScript, ensuring the script is explicitly located and validated. This change was applied in both frontend/public/widget.js and frontend/src/embed/widget.js for consistency. [1] [2]
• Modified the embedScript in the WidgetEditor component to include the id="hievent-widget-script" attribute, aligning it with the updated script identification logic.

(sorry for the import re-organise):

• imports in frontend/src/components/common/WidgetEditor/index.tsx re-ordered. I opened Hi.Events in the wrong IDE Workspace (sorry!).