docs(readme): 加 i18n 切换 + 新增英文版 + Releases 统一指向 Gitea

- 顶部加'简体中文 | English'切换 header
- 下载链路统一指 Gitea Releases:Gitea 是 source of truth(推 GitHub
  靠 push mirror 兜底),不再列 GitHub Releases 让外部读者多一跳
- 自行构建段如实写'GitHub Actions 构建 → Gitea API 同步发布':build
  在 windows-latest 跑 PyInstaller,然后由 sync step 把 artifact
  推到 Gitea Releases(.github/workflows/release.yml + .gitea
  /workflows/release.yml noop 占位)
- 新增 README.en.md

README.en.md

@@ -0,0 +1,78 @@
+# df-scope-hold
+
+[简体中文](README.md) | English
+
+Auto-hold-breath helper for Delta Force — while you hold the right mouse
+button, the tool presses a configurable key (default `F12`) and releases it
+when you let go. Aim with right-click only; no extra key press needed.
+
+## How it works
+
+Pure local mouse→keyboard mapping. The script listens for right-mouse-button
+events and presses/releases your configured "hold breath" key in sync. It
+activates only while the game process is running. **No game memory is read,
+no game files are modified, no game-server traffic is involved** — the
+behavior is equivalent to a hardware mouse macro.
+
+The in-game "hold breath" binding must be set to **hold mode**, not toggle
+mode, or the simulated key release on right-mouse-up will get out of sync
+with the game's scope state.
+
+## Usage
+
+1. **Bind "hold breath" in-game** to a key that does not conflict with other
+   actions (e.g. `F12`).
+2. **Download** the latest `df-scope-hold-vX.X.X.zip` from [Gitea Releases](https://git.zhengchentao.win/zhengchen.tao/df-scope-hold/releases) and unzip anywhere.
+3. **Edit `config.ini`** so `key` matches the in-game binding.
+4. **Run `df-scope-hold.exe`**. UAC will prompt for admin privileges — accept,
+   as the anti-cheat-protected game process is otherwise undetectable.
+
+```ini
+[config]
+key = f12                                              ; must match in-game binding
+delay_press = 5                                        ; ms between RMB-down and simulated key-down
+program_running = DeltaForceClient-Win64-Shipping.exe  ; game process name (case-sensitive)
+```
+
+Press `Ctrl+C` in the console to exit.
+
+## Runtime
+
+Single Windows `.exe` (~10 MB), built with PyInstaller — bundles the Python
+runtime and dependencies (`pynput`, `psutil`). No Python install required.
+
+Verified on Windows only (the Delta Force client is Windows-exclusive).
+
+## From source
+
+```bash
+pip install -r requirements.txt
+python script.py
+```
+
+Requires Python 3.10+. For day-to-day use, just download a release.
+
+## Build
+
+```bash
+pip install -r requirements.txt
+pyinstaller --onefile --uac-admin --console --name df-scope-hold script.py
+```
+
+Output at `dist/df-scope-hold.exe`. GitHub Actions builds on `windows-latest`
+(see `.github/workflows/release.yml`) when you push a `v*` tag, then syncs
+the artifact to [Gitea Releases](https://git.zhengchentao.win/zhengchen.tao/df-scope-hold/releases)
+via the Gitea API — no local build needed.
+
+## Disclaimer
+
+- This is a purely local mouse→keyboard mapping tool, functionally identical
+  to the macro feature of any gaming mouse.
+- That said, the game publisher's policy on third-party input tools may
+  change. **Any consequences from using this tool (including but not limited
+  to account bans) are at the user's own risk.**
+- For personal use and learning only. Do not use in ranked / competitive play.
+
+## License
+
+MIT