proposal: renovate presets for Earthfiles

[janishorsts]

Use case

@gilescope suggested:

It would be nice to have @renovate presets for Earthfiles.

@renovate has a specification for defining preset files https://docs.renovatebot.com/config-presets/#preset-file-naming

Expected Behavior

Something like...

{
   "extends": ["github>EarthBuild/earthbuild"]
}