[wip]add namingserver-combined-with-raft.md blog

[funky-eyes]

What is the purpose of the change

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Brief changelog

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Follow this checklist to help us incorporate your contribution quickly and easily:

• Make sure there is a GITHUB_issue filed for the change(usually before you start working on it). Trivial changes such as typos do not necessitate a GITHUB issue. Your pull request should solely focus on addressing this specific issue without incorporating any other modifications. Each PR should resolve a single issue.
• Format the pull request title like doc: add an operations guide document. Each commit within the pull request should contain a meaningful subject line and body.
• Write a pull request description that is detailed enough to understand what the pull request does, how, and why.
• Test your code locally by running npm run build, and make sure it works as expected.
• Ensure that no files under the build folder are included in the commit, as well as the package-lock.json and yarn.lock files.