refactor(css): seperate active-heading-font-color from active-font-color

[natowb]

Pull Request Description

Currently working on adding support for this plugin with my theme and stumbled into this issue. statblocks sets a css variable called ---statblock-heading-font-color however it doesn't seem to be used when settting the --active--heading-font-color

we don't lose any existing functionality or break existing styles as --statblock-heading-font-color defaults to --statblock-font-color which defaults to --statblock-primary-color. this mimics the functionality that --active-font-color has as well.

src/main.css

--statblock-primary-color: #7a200d;
[ ... ]
--statblock-font-color: var(--statblock-primary-color);
[ ... ]
--statblock-heading-font-color: var(--statblock-font-color);

src/view/Statblock.svelte

--active--font-color: var(
    --statblock-font-color,
    --active--primary-color
);

Changes Proposed

• [x] sets --active--heading-font-color to --statblock-heading-font-color instead of --active--font-color

Related Issues

N/A

Checklist

• [x] I have read the contribution guidelines and code of conduct.
• [x] I have tested the changes locally and they are working as expected.
• [x] I have added appropriate comments and documentation for the code changes.
• [x] My code follows the coding style and standards of this project.
• [x] I have rebased my branch on the latest main (or master) branch.
• [x] All tests (if applicable) have passed successfully.
• [x] I have run linters and fixed any issues.
• [x] I have checked for any potential security issues or vulnerabilities.

Screenshots (if applicable)

if i set --statblock-heading-font-color to #00c2a8 I would expect the heading to change color.

Current	With Changes

Additional Notes

N/A