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/rollup.config.js b/rollup.config.js
index f321c2e..5fba701 100644
--- a/rollup.config.js
+++ b/rollup.config.js
@@ -19,7 +19,7 @@
 import run from '@rollup/plugin-run';
 import typescript from '@rollup/plugin-typescript';
 
-const dev = process.env.NODE_ENV !== 'production';
+const dev = !!process.env.ROLLUP_WATCH;
 
 export default (async () => ({
   input: 'app.ts',