Add yaohe (open-source project promotion plugin)

[nmhjklnm]

Adds yaohe (吆喝) to Marketing Growth — a plugin that lets your agent promote an open-source project across 20 CN & EN channels (ruanyf/weekly, HelloGitHub, Show HN, awesome lists, dev.to, …), with per-channel tailored copy and rule-abiding tiered automation (issue/PR channels auto-submit via gh; community posts are drafted but never auto-posted).

Repo: https://github.com/nmhjklnm/yaohe (MIT)

Vendored the plugin per this repo's convention (plugins/yaohe/) and added the entry to both README.md and README-zh.md in list style.

[nmhjklnm]

Self-review before maintainer review — two findings, both fixed in 51f81f4:

1. marketplace.json missing entry (CONFIRMED): the plugin was vendored and listed in both READMEs but not registered in .claude-plugin/marketplace.json, so claude plugin install yaohe would fail. Added the entry following the existing schema.
2. Alphabetical order : the README entries were inserted between tiktok-strategist and twitter-engager; moved after twitter-engager in both README.md and README-zh.md.

Also verified: all relative links inside plugins/yaohe/ resolve, banner image uses an absolute raw URL (HTTP 200), plugin.json is valid JSON matching the conventions of existing vendored plugins, no runtime artifacts vendored.