Add npm workspaces at the root package.json

Various improvements to make jami-web a monorepo.
Update scripts in package.json
Add npm workspaces and root dependency to "concurrently". This makes it possible to start everything from the
root. For example, one can run `npm run build --workspaces` to build all
workspaces, or `npm run build --workspace client` to build only the
client.

GitLab: #54
Change-Id: Iee777165188db0229c042cb7bb75d55dff8d2fec
diff --git a/server/package.json b/server/package.json
index d73d427..1c88fcd 100644
--- a/server/package.json
+++ b/server/package.json
@@ -5,7 +5,7 @@
     "start": "nodemon --watch src src/index.ts",
     "start:prod": "env NODE_ENV=production node dist/index.js",
     "build": "tsc",
-    "clean": "rm -Rf dist",
+    "clean": "rm -Rf dist tsconfig.tsbuildinfo",
     "lint": "eslint src",
     "lint:fix": "eslint --fix src",
     "format": "prettier --write src",