Make Jitsi download script a JS script

It's awful but means that we create the directory on all platforms in-process.

Fixes https://github.com/vector-im/riot-web/issues/13215

package.json

@@ -38,7 +38,7 @@
     "clean": "rimraf lib webapp electron_app/dist",
     "build": "yarn clean && yarn build:genfiles && yarn build:compile && yarn build:types && yarn build:bundle",
     "build-stats": "yarn clean && yarn build:genfiles && yarn build:compile && yarn build:types && yarn build:bundle-stats",
-    "build:jitsi": "scripts/build-jitsi.sh",
+    "build:jitsi": "node scripts/build-jitsi.js",
     "build:res": "node scripts/copy-res.js",
     "build:genfiles": "yarn reskindex && yarn build:res && yarn build:jitsi",
     "build:modernizr": "modernizr -c .modernizr.json -d src/vector/modernizr.js",
@@ -135,6 +135,7 @@
     "minimist": "^1.2.0",
     "mkdirp": "^0.5.1",
     "modernizr": "^3.6.0",
+    "node-fetch": "^2.6.0",
     "optimize-css-assets-webpack-plugin": "^5.0.3",
     "postcss-extend": "^1.0.5",
     "postcss-hexrgba": "^2.0.0",