docs: refresh example catalog and links

[GuangmingLuo]

What changed

• Remove the stale tracer entry that points to a deleted directory.
• Add the current route, opentelemetry, and built-in sse examples.
• Correct the gpress description and clarify the TLS, rendering, routing, monitoring, reverse proxy, and client examples.
• Replace external middleware links whose example subpaths are no longer present with confirmed repository or file entry points.
• Keep the English and Chinese README catalogs aligned and remove the duplicate gzip entry.

Why

The root README had drifted from the repository: one local link was dead, several newer examples were missing, one external project description was outdated, and some descriptions no longer matched the example contents.

Validation

• Checked all relative links in README.md and README_CN.md against the checkout.
• Checked the diff with git diff --check.
• Verified the external GitHub repository/file targets through the GitHub connector.