docs: Add markdown header to docs

[patrycjakalinska]

Few docs were missing markdown header - instead they had docusaurus title property. Because of that it wasn't possible to generate og images for them. In the future these docs will be rewritten to meet current style guide.

That's why we decided to add # Title in docs instead of fix for title: ... in generate-og-images.js script. If we were to add fix to the script it will become redundant within a month or two.

Following docs were added a header:

• interpolateColor
• Debugging worklets
• Testing with Jest