Add documentation on mechanisms for node monitoring and protection

[BigLep]

Done Criteria

1. There is an easily discoverable way for a js-libp2p node operator to find the monitoring options available to them
2. We have a document we can point js-libp2p operators to in defense of or response to various resource exhaustion attacks (DoS, eclipse).

Why Important

1. These are concepts that are best thought about in advance to prevent successful attacks.
2. If there is an attack, especially in the heat of battle, every minute reducing response/mitigation times can be significant. Having suggestions/steps prethought outside the fog of war will provide better suggestions in a quicker period of time.

Background

1. js-libp2p has various mechanisms to protect a node against attacks. We want to make sure users are aware of the mechanisms available to them and that they're thinking about this.
2. go-libp2p and rust-libp2p used libp2p/docs as the entry point: Guide for how to respond to resource exhaustion attacks docs#153. js-libp2p can follow the same.
3. These need to get publicly documented in an easily discoverable place.

To-do

• Update docs for monitoring docs: update metrics docs #1441
• Update DoS mitigation page docs: add js-libp2p discussion to dos mitigation page docs#205
• address comments in docs: add limit configuration documentation #1421 that came in after merging.
  These are partially covered in docs: update limits doc #1456.

[p-shahi]

This item is completed. Some more docs (doc/LIMITS.md) will be updated as a part of #1508 but not a reason to keep this open