Document launchNode method

[arboleya]

Consider [exporting the utility] and documenting how to launch a fuel-core node programmatically.

Very similar to what we did with the launchTetNode utility in #1356:

• https://docs.fuel.network/docs/fuels-ts/testing/launching-a-test-node/

[danielbate]

Why would someone want to use this over the fuels node command. Or just running directly from their fuel-core install. Just wondering if this does have value outside of launchTestNode?

[arboleya]

Because they might want to use it programmatically. I think it'd be more helpful for people using custom scripts to set up their env. Yes, they could interact with the binaries directly, but that wouldn't be as straightforward as using the utility via typescript.

When inside a test context, launchTestNode should suffice.