Electron app loading improvements + Windows paths fix (#429)

- Electron no longer allows Windows paths in URLs
(https://www.electronjs.org/docs/latest/breaking-changes#behavior-changed-custom-protocol-url-handling-on-windows),
fixes with help of wabac.js to replace `C:\path\to\file` with
`C//path/to/file`
- Electron app cleanup: replace deprecated protocol handlers with new
protocol.handle() method, update types
- Electron app: ensure just filename is displayed on index page,
consistent with other platforms
- Update to wabac.js 2.23.2
- Update to Electron 36.3.2
- Fixes #427
- bump to 2.3.12

tsconfig.json

@@ -2,6 +2,7 @@
   "compilerOptions": {
     "outDir": "./dist/",
     "module": "esnext",
+    "lib": ["esnext", "dom", "dom.iterable"],
     "target": "es6",
     "moduleResolution": "Bundler",
     "allowJs": true,