feat(accordion-panel): Updated icon section to a separate template

[drakkaroy]

Description

This update allow overwrite in an easy way the icon, as usually we extend outline-accordion and create custom styles in a new component but if we want change the icon we should overwrite all the render function, with a template we can just overwrite this template.

Type of change

• [x] New feature (non-breaking change which adds functionality)

How Has This Been Tested?

• [x] Visual Testing

Checklist

• [x] My code follows the style guidelines of this project
• [x] I have performed a self-review of my own code
• [x] I have commented my code, particularly in hard-to-understand areas
• [ ] I have made corresponding changes to the documentation
• [x] My changes generate no new warnings
• [ ] I have added tests that prove my fix is effective or that my feature works
• [ ] New and existing unit tests pass locally with my changes
• [ ] Any dependent changes have been merged and published in downstream modules

[damontgomery]

@drakkaroy implemented this on a project we're on where we just wanted to updates styles including the icons used. Styles were easy enough by redefining the CSS to use in the class, but this was helpful to avoid a complete overwrite of the render method.