feat: new enabled flag

[aldenquimby]

This is my first PR, so please let me know if there's anything else you'd like to see in terms of docs or tests!

Why

• "official" fix for #8

How

• new enabled config option is a flexible way to allow users to turn off plugin with invoke local
• this is a common way to approach the problem, e.g. see serverless-domain-manager

[aldenquimby]

@thomasmichaelwallace how does this PR look? My team is excited to use better-credentials once we have this flag. Thank you!

[thomasmichaelwallace]

@aldenquimby take a look at my suggestion - that .custom is not a guaranteed key.

And then we're good to go I think.

[aldenquimby]

@thomasmichaelwallace I don't see your suggestion, but I can guess at it based on that comment! Just pushed an update that makes .custom optional

[aldenquimby]

Thanks @thomasmichaelwallace ! Excited for this to release 🚀

[thomasmichaelwallace]

Now released - https://github.com/thomasmichaelwallace/serverless-better-credentials/releases/tag/v1.3.0

[aldenquimby]

@thomasmichaelwallace thank you! Just upgraded and it looks good