Add Mise documentation and reference it in README

Author: alanrrb

Mise.md

@@ -0,0 +1,41 @@
+# Mise
+
+[mise](https://mise.jdx.dev) is a polyglot runtime manager (Ruby, Node.js, Python, Go, and more). It replaces tools like rbenv, nvm, and pyenv with a single CLI.
+
+## Common commands
+
+| Command | Action |
+|---|---|
+| `mise use --global ruby@3.3` | Set global Ruby version to 3.3 |
+| `mise use ruby@3.2` | Set Ruby 3.2 for the current project (creates `.mise.toml`) |
+| `mise use --global node@22` | Set global Node.js version to 22 |
+| `mise install ruby node` | Install the configured versions |
+| `mise current` | Show active tool versions |
+| `mise ls` | List all installed versions |
+| `mise ls-remote ruby` | List available Ruby versions |
+| `mise upgrade ruby` | Upgrade Ruby to the latest compatible version |
+| `mise prune` | Remove unused versions to free disk space |
+
+## Per-project versions
+
+Create a `.mise.toml` in your project root to pin versions:
+
+```toml
+[tools]
+ruby = "3.3"
+node = "22"
+```
+
+Mise picks this up automatically when you `cd` into the project directory.
+
+## Adding more tools
+
+Mise supports many tools beyond Ruby and Node.js:
+
+```bash
+mise use --global python@3.12
+mise use --global jq
+mise use --global go@latest
+```
+
+See the full list with `mise registry` or at [mise.jdx.dev](https://mise.jdx.dev).

README.md

@@ -86,6 +86,7 @@ Every config file sources a `.local` counterpart if present. Place your personal
 
 - [Vim Key Mapping](Vim.md)
 - [Tmux Key Mapping](Tmux.md)
+- [Mise](Mise.md)
 - [Testing](tests/README.md)
 
 ## Options