Add electron support

Start with the examples/electron entry point and the call to BrowserWindow.addDevToolsExtension(path), then compare the Electron API documentation with the reported stack trace. Done means the Dirac extension can be loaded in the Electron example without the undefined path error.

Hello! I'm playing around with shadow-cljs + electron (which seems to work really nice!). dirac seems like it would benefit me greatly, so I tried adding it using electrons BrowserWindow.addDevToolsExtension(path) (api docs here).
Sadly I get this error, and I'm unable to figure out what's going wrong:

Uncaught Exception:
TypeError [ERR_INVALID_ARG_TYPE] [ERR_INVALID_ARG_TYPE]: The "path" argument must be of type string. Received type undefined
    at validateString (internal/validators.js:105:11)
    at Object.join (path.js:1037:7)
    at startBackgroundPages (/Users/<omitted>/examples/electron/node_modules/electron/dist/Electron.app/Contents/Resources/electron.asar/browser/chrome-extension.js:80:33)
    at loadExtension (/Users/<omitted>/examples/electron/node_modules/electron/dist/Electron.app/Contents/Resources/electron.asar/browser/chrome-extension.js:288:3)
    at Function.BrowserWindow.addExtension (/Users/<omitted>/examples/electron/node_modules/electron/dist/Electron.app/Contents/Resources/electron.asar/browser/chrome-extension.js:378:7)
    at Function.BrowserWindow.addDevToolsExtension (/Users/<omitted>/examples/electron/node_modules/electron/dist/Electron.app/Contents/Resources/electron.asar/browser/chrome-extension.js:408:40)
    at Object.example$main$create_window [as create_window] (/Users/<omitted>/examples/electron/.shadow-cljs/builds/main/dev/out/cljs-runtime/example.main.js:30:46)
    at App.example$main$maybe_create_window (/Users/<omitted>/examples/electron/.shadow-cljs/builds/main/dev/out/cljs-runtime/example/main.cljs:51:3)
    at App.emit (events.js:194:13)

I've successfully used the react dev tools extension, so I don't think I'm doing anything wrong on my end.

Any help or suggestions is very appreciated. :)