Enable loading price data over plain HTTP

[reddog]

Switch method to load price data.

New solution pattern:

• Code in index.html to load current prices switched from fetch to defining a script tag.
• script tag is added after the DOM has loaded to ensure JS in index.html is available.
• Handler function defined in index.html is called by the current prices JS script (current-v1.js)
• Build script for prices data files enhanced to create a JavaScript version (in addition to the previous JSON version)
  • Current prices JS file augmented to call the handler defined in index.html

Processing follows this flow:

• index.html is loaded in the browser
• In JS in index.html, we wait until the DOM has loaded and then we:
  • Define logic to parse model prices (effectively this is unchanged)
  • Declare a handler to parse model prices
  • Create a script tag to load current-v1.js
• Script current-v1.js will be loaded
  • current-v1.js is enclosed in a IIFE to protect itself and other scripts
  • Model price data is defined
  • Handler function defined in index.html is called to parse model prices - this continues the usual process flow.

Previous method uses JS fetch. This fails in Chrome when loading the file locally with a CORS Schema error.

Anticipated benefit is that users can run the web page locally for development / usage purposes.

Previously Chrome error was;

Access to fetch at 'file:///local-directory-path/current-v1.json' from origin 'null' has been blocked by CORS policy: Cross origin requests are only supported for protocol schemes: chrome, chrome-extension, chrome-untrusted, data, http, https, isolated-app.