Add Pi installation instructions

Pi now supported alongside Claude Code, Codex, Cursor, and Gemini CLI.
Matches nutrient-skills PR #7.

Author: jdrhyne

README.md

@@ -22,19 +22,25 @@ Fast, accurate Markdown from PDFs — locally, with no cleanup required. Built f
 
 ### Agent skill (recommended)
 
-If you use Claude Code, Codex, Cursor, or Gemini CLI, install the [Nutrient Skills](https://github.com/pspdfkit-labs/nutrient-skills) plugin — the extraction runs automatically when your agent needs to read a PDF:
+If you use Claude Code, Codex, Pi, Cursor, or Gemini CLI, install the [Nutrient Skills](https://github.com/pspdfkit-labs/nutrient-skills) plugin — the extraction runs automatically when your agent needs to read a PDF:
 
 ```bash
 npx skills add pspdfkit-labs/nutrient-skills --skill pdf-to-markdown
 ```
 
-Or with marketplace/plugin flows:
+Or with marketplace/plugin flows (Claude Code, Codex):
 
 ```text
 /plugin marketplace add pspdfkit-labs/nutrient-skills
 /plugin install pdf-to-markdown@nutrient-skills
 ```
 
+With Pi:
+
+```bash
+pi install git:github.com/PSPDFKit-labs/nutrient-skills
+```
+
 Once installed, just reference a PDF in your prompt — no extra commands needed:
 
 > "Extract the pricing table from proposal.pdf"