Contrast issue in the demo page hero header

[Azizham66]

Description
The header text "Supports full Markdown specifications." in the hero section of the demo page has a light color that is not readable because of the light color background.

Reproduction

if you select the text you see this:

Steps
To reproduce the behavior:

1. Go to 'wysimark.com'
2. Scroll down to the demo
3. Select the hero header to see the text
4. See error

Expectation
A readable black (or other dark color) contrasting with the background color.

Environment

• Wysimark Version: [e.g. 1.0.55]
• Operating System: [e.g. Windows]
• Browser: [e.g. Chrome, Safari]
• TypeScript Version: [e.g. 3.9.7 - required only if it's a TypeScript issue]

[Azizham66]

I can fix the issue