Add support for multiple tunnels simultaneously

[amalshaji]

⚠️ Breaking change

This PR breaks the client config format. It introduces a new field to the config, tunnels, describing multiple tunnel connections.

target: wss://x.amal.sh
secretkey: ThisIsASecret
tunnels:
  - name: tp1
    subdomain:
    port: 8000
  - name: tp2
    subdomain:
    port: 9000

Demo

Here, the subdomains are left empty