Add mirai skill and instructions (#576)

Author: shikokuchuo

dev/skills/README.md

@@ -0,0 +1,51 @@
+# mirai Skill for Agents
+
+The mirai skill for async, parallel, and distributed computing in R is part of the [posit-dev/skills](https://github.com/posit-dev/skills) repository, a collection of Claude Skills from Posit for R package development, Shiny, Quarto, and more.
+
+## Installation
+
+### Using `npx skills add` (Any Agent)
+
+Works with Claude Code, Codex, Cursor, Cline, and [other supported agents](https://github.com/vercel-labs/skills).
+
+```bash
+# Install just the mirai skill
+npx skills add posit-dev/skills --skill mirai
+
+# Browse and install interactively
+npx skills add posit-dev/skills --all
+```
+
+### Using Claude Code Plugins
+
+#### Add the Posit marketplace (recommended)
+
+Adding the marketplace lets you browse and install any skill, and easily update them later.
+
+```bash
+# Add the marketplace
+claude plugin marketplace add posit-dev/skills
+
+# Install the r-lib category (includes mirai and all R package dev skills)
+claude plugin install r-lib@posit-dev-skills
+```
+
+#### Direct install without marketplace
+
+```bash
+claude plugin install r-lib@posit-dev-skills
+```
+
+## Updating
+
+Skills installed via the Claude Code plugin system can be updated:
+
+```bash
+# Update the marketplace index first
+claude plugin marketplace update
+
+# Then update individual plugins (use the same plugin@marketplace identifier as install)
+claude plugin update r-lib@posit-dev-skills
+```
+
+Skills installed via `npx skills add` are copied into your agent's configuration at install time. To update, simply re-run the install command to fetch the latest versions.