add instructions for contributions

Author: zerosnacks

README.md

@@ -1,3 +1,15 @@
 # Browser wallet
 
 Interface for interacting with Foundry from the browser.
+
+### Development
+
+```
+curl -fsSL https://get.pnpm.io/install.sh | sh - # Install pnpm
+pnpm install # Install dependencies
+pnpm dev # Start interface on a development server
+```
+
+When running Foundry pass the `--browser-disable-open` and `--browser-development` flags.
+
+The `--browser-development` flag disables certain security policies allowing you to connect from `localhost:5173`, the port selected by Vite.