Add page for changing the eopkg configuration

[EbonJaeger]

Description

This adds a page detailing how to modify the default eopkg configuration.

Submitter Checklist

• [ ] Squashed commits with git rebase -i (if needed)

[davidjharder]

I would add a sentence or two explaining what is using eopkg.conf Here you're aiming to control solbuild right?

[davidjharder]

Josh: You want to merge this? Alternatively I can