chore: drop trailing keyword block from README

[OussemaFr]

What

Removes the 12-keyword <sub> block at the bottom of README.md.

Why

Two reasons:

1. Looks AI-spammy. A trailing keyword list at the end of a README is the textbook keyword-stuffing pattern Google's algorithm now penalizes. Modern hand-written READMEs almost never have these.
2. It's redundant. Every important search term — facebook-scraper, kevinzg, facebook api alternative, instagram-scraper — already appears naturally in the README prose and section headings. Google ranks those in-context mentions higher anyway.

What handles SEO instead

Search surface	How it's covered
Google (repo page indexing)	Natural keyword mentions throughout README sections
GitHub's own search	Repo About → Topics (set in repo settings)
Both	Repo About → Description

So no SEO is actually lost — just the spammy-looking footer.

Test plan

• README still renders cleanly to the License section
• No reference to the keyword block in any other file (grep confirms)