Steps to running watchers

[luketchang]

Outline steps to running watchers given current agents setup for external parties. Something along the lines of:

1. Enroll their preferred watcher addresses on desired chains.
2. Write custom config that just includes desired networks (e.g. running watcher over Evmos <> Eth would only include those two networks).
3. Have party run one watcher per home-outward-direction(s) they are watching (e.g. Evmos <> Eth would have one watcher for each direction).

[yourbuddyconner]

Note: this should be included as a portion of a larger "How 2 Run Agents" doc