docs: add Simplified Chinese README translation (README_zh.md)

[WanderLandWalker]

What this does

Adds a Simplified Chinese translation of the README as README_zh.md to help Chinese-speaking developers discover and adopt lnav.

• Purely additive: one new file, no existing files modified.
• Preserved unchanged: the source's first-line HTML comment <!-- This is a comment for testing purposes --> verbatim (in the translation it sits on line 3, just under the added banner; it is the source's own testing comment); the badge lines themselves byte-identical — the badge URL query parts (percent-encoded workflow%3Aci-build and Ask%20LNAV%20Guru-006BFF, plus plain badge/?version=latest&style=plastic and ?branch=master appearing twice); the raw-HTML Discord link line <img src="https://assets-global.website-files.com/…" height="20" alt="Discord Logo"/> inside its […](https://discord.gg/erBPnKwz7R) wrapper; the screenshot construct [![Screenshot](docs/assets/images/lnav-front-page.png)](docs/assets/images/lnav-front-page.png) including the Screenshot alt and both relative targets; all 10 fenced code blocks byte-for-byte (the four console blocks — $ brew install lnav, $ pkg install lnav, $ lnav /path/to/file1 /path/to/dir ..., and the $ ./configure / $ make / $ sudo make install block — plus the six unnamed ``` journalctl-pipe blocks with their flags and the long --output-fields=MESSAGE,PRIORITY,_PID,SYSLOG_IDENTIFIER,_SYSTEMD_UNIT line); every inline-code identifier in prose (`e`/`E`, `/`, `:highlight`, `P`, `i`, `;`, `j`/`k`/`h`/`l`, `tail`/`grep`/`less`, the two ssh-command display spans `$ ssh playground@demo.lnav.org` / `` `$ ssh tutorial1@demo.lnav.org` ``, `lnav`, `journalctl`, `systemd-journald`, `-a`, `-b`, `-n`, `--since=...`, `t`, `./autogen.sh`); the markdown-escaped `_SYSTEMD_UNIT` in prose (backslash kept); the `[^1]:` footnote marker with its 6-space-indented continuation line structure; all URL fragments inside absolute links (`#json-lines`, `#spatial-navigation` ×2, `#highlight-pattern`, `#regular-expression-match`, `#sqlite-expression`, `#pretty`, `#hist`, `releases/latest#release-artifacts`, `…/sqlext.html`); the `ssh://` and `mailto:` scheme URLs; the relative `ARCHITECTURE.md` target; the column padding of the prerequisites list (`gcc/clang - `, `libpcre2 - `, … — only the description after the dash was translated); version numbers (C++14, SQLite 3.9.0, libcurl 7.23.0, systemd v236); and proper nouns (LNAV/lnav, Discord, Homebrew/Brew, FreeBSD, MacOS, Unix, SQLite, PRQL, PCRE2, zlib/bz2/libarchive/libunistring, 'tshark'/pcap, syslog, Google Groups, SignPath.io/SignPath Foundation, Anthropic, Claude for Open Source Program, SumoLogic, Angle-grinder, GitHub Sponsors, Read the Docs, LOG/TEXT "Files" view names).
• The source README contains no in-page ](#…) anchor links (its TOC-style links are absolute URLs to docs.lnav.org, which is why fragments live inside full URLs), so nothing needed to be pinned.
• Translated: the prose (heading kept the product name: # LNAV —— 日志文件导航器), section headings, the prerequisites/feature bullets' descriptions, link display text (e.g. [美化打印 JSON-lines](…), [主站](…), [内部架构](…) — with [**文档**] keeping its inner bold), and the footnote definition sentence (its [^1]: marker and indentation kept).
• A top banner links back to the canonical English README.md.

Note on AI assistance

This translation was produced with AI assistance and independently reviewed for accuracy, formatting, and compliance before submission. The project is BSD-2-Clause licensed.

Becoming a Contributor

I checked for contribution policy files: CONTRIBUTING.md (repo root, .github/, and docs/) and a PR template all return 404, the README's own "Contributing" section only links the GitHub Sponsors page, and there is no AI/LLM prohibition, DCO, or CLA anywhere in the repo's contributor-facing docs — so this purely additive translation follows the normal fork → pull-request flow. I would love to become a Contributor to this repository, and I'm happy to match any preferred convention and keep the translation in sync as the English README evolves.