fix: price parsing with currency symbol

[Soare-Robert-Daniel]

Summary

• Add a better parsing for pricing.

Will affect visual aspect of the product

NO

Test instructions

• Go to edit a product and add a PPOM field (e.g. text input), and set the 'Addon price' field to "$10" (or any non-numeric string like "10abc").
• Save and add it to a product and check the front end.
• There should be no fatal error.

Check before Pull Request is ready:

• I have written a test and included it in this PR
• I have run all tests and they pass
• The code passes when running the PHP CodeSniffer
• Code meets WordPress Coding Standards for PHP, HTML, CSS and JS
• Security and Sanitization requirements have been followed
• I have assigned a reviewer or two to review this PR (if you're not sure who to assign, we can do this step for you)

Closes https://github.com/Codeinwp/ppom-pro/issues/642

[pirate-bot]

Tip

You can preview the changes in the Playground

Plugin build for a91f96f is ready 🛎️!

• Download PPOM - build 🔗