Add polymm project to arbitrage tools list (#152)

Adds polymm under Alpha Collections > Arbitrage (Crypto).

polymm is an MIT-licensed Python market-making/arbitrage bot for Polymarket (Polygon/USDC) sports and esports markets. It de-vigs sportsbook odds to compute fair value, posts passive limit orders on the CLOB, and hedges the opposite leg. Ships with wallet analytics scripts that work against any public Polymarket wallet.

The arbitrage section notes the existing bots are old and unmaintained - this one is current and documented, with a full public track record:

https://kacho.io/polymarket-arbitrage-real-numbers
Wallet: https://polymarket.com/@b00k13

Happy to move it to Backtest + live trading > Crypto currency focus if you think that's a better fit.

Readme.md

@@ -231,6 +231,7 @@ Note: the one marked as `Live Trading` has reasonable live trading support for a
 - [Blackbird](https://github.com/butor/blackbird) | `C++` | - Blackbird Bitcoin Arbitrage: a long/short market-neutral strategy
 - [bitcoin-arbitrage](https://github.com/maxme/bitcoin-arbitrage) | `Python` | - Bitcoin arbitrage - opportunity detector
 - [R2 Bitcoin Arbitrager](https://github.com/bitrinjani/r2) | `TypeScript` | - R2 Bitcoin Arbitrager is an automatic arbitrage trading system powered by Node.js + TypeScript.
+- [polymm](https://github.com/kachence/polymm) ![GitHub last commit](https://img.shields.io/github/last-commit/kachence/polymm/main) ![GitHub Repo stars](https://img.shields.io/github/stars/kachence/polymm?style=social) | `Python` | - Market-making and arbitrage bot for Polymarket sports markets. De-vigs sportsbook odds to a fair price, quotes passively on the CLOB, and hedges the opposite side. Includes wallet analytics scripts that run against any public Polymarket wallet.
 
 ## Basic Components