Add completion for uv Python package manager (#1071)

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Author: hongquan

custom-completions/uv/README.md

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+# uv completions
+
+[uv](https://docs.astral.sh/uv/) is a Python package and project manager, known for its speed.
+
+Though `uv` can generate its Nu completion script via `uv generate-shell-completion`, this script can only
+provide static choices, not dynamic choices from _pyproject.toml_ file.
+
+## Install completion script
+
+First, if you installed the script generated by `uv generate-shell-completion`, please remove it to avoid conflict.
+
+### Method 1: Use from Git repo
+
+- `git clone https://github.com/nushell/nu_scripts.git`
+
+- Add this to `$nu.config-path` file.
+
+  ```nu
+  source repo/custom-completions/uv/uv-completions.nu
+  ```
+
+### Method 2: Selectively copy
+
+
+- Copy the _uv-completions.nu_ to Nu standard place.
+
+  ```nu
+  cp custom-completions/uv/uv-completions.nu ($nu.data-dir | path join 'completions')
+  ```
+
+- Open `$nu.config-path` file and add this:
+
+  ```nu
+  source uv-completions.nu
+  ```