docs: add Buy Me a Coffee funding link and README button

Author: MattDevy

.github/FUNDING.yml

@@ -1 +1 @@
-github: [MattDevy] # Replace with up to 4 GitHub Sponsors-enabled usernames e.g., [user1, user2]
+buy_me_a_coffee: MattDevy

README.md

@@ -6,6 +6,10 @@
 [![npm](https://img.shields.io/npm/v/pi-continuous-learning)](https://www.npmjs.com/package/pi-continuous-learning)
 [![License: MIT](https://img.shields.io/badge/License-MIT-yellow.svg)](LICENSE)
 
+<!-- markdownlint-disable MD033 -->
+<script type="text/javascript" src="https://cdnjs.buymeacoffee.com/1.0.0/button.prod.min.js" data-name="bmc-button" data-slug="MattDevy" data-color="#FF5F5F" data-emoji=""  data-font="Cookie" data-text="Buy me a coffee" data-outline-color="#000000" data-font-color="#ffffff" data-coffee-color="#FFDD00" ></script>
+<!-- markdownlint-enable MD033 -->
+
 Inspired by [everything-claude-code/continuous-learning-v2](https://github.com/nicholasb/everything-claude-code), reimplemented as a native Pi extension in TypeScript.
 
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