Add SkimReaderTool: x402-native pay-per-call web reader

Feature request

Add a new tool, `SkimReaderTool`, to `crewai-tools`.

**What it does:** given any URL, it returns clean, agent-ready Markdown (nav/ads/boilerplate stripped) plus structured metadata (title, byline, published date, language, excerpt).

**Why it's a good fit:** crewAI already ships several scraping/reader tools (e.g. `FirecrawlScrapeWebsiteTool`), but none are pay-per-call over an open payment rail. `SkimReaderTool` is built on the [x402](https://x402.org) protocol — each read costs $0.002 in USDC on Base, paid automatically by a wallet the user controls. No signup, no API keys; the wallet is the identity, and the private key never leaves the user's machine.

A working implementation already exists and is ready for review: #6264 (previously closed only because it predated the first-time-contributor issue-link requirement — reopening now to reference this issue).