Add "external coordinators" to the federated client.

[Reckless-Satoshi]

Is your feature request related to a problem? Please describe.
P2P liquidity remains very fragmented. Power users of p2p typically use several platforms at the same time.

Describe the solution you'd like
Now that the RoboSats client v0.6.0 is suitable to display orders in the order book from many different robosats coordinators, we could also add "external coordinators", such as, HodlHodl, Bisq, Peach, lnp2pbot or Mostro. These could be disabled/enabled by the user at will. Clicking on an offer hosted by, for example, Hodlhodl, will show the user some offer details and a button to visit such offer in hodlhodl.com with a warning that he is about to leave RoboSats and privacy might be degraded.

Additional context
I propose we start by adding HodlHodl as the first external coordinator as the API is clear and concise. The number of orders that can be fetched at once is limited to 100. Therefore, if no filter is applied by the user (by currency, by sell/buy, or by payment method) not all orders will be displayed.

Adding any: Hodlhodl, Bisq, Peach or @lnp2pBot offers to the federation frontend is a task rewarded with ⚡ 1.5M Sats ⚡ (Each of them, so 4 rewards in total).

Other
To be discussed is whether it is ethical and private to use a referral link for the external services. If these are used, we could more easily fund RoboSats development and in some cases, the users will get a lower fee. In any case, privacy must remain the top priority. Referral links will always be disclosed.