Support excluding endpoints

[mortocks]

Add ability to exclude collections or endpoints from the spec including

• payload preferences
• payload migrations
• custom collections
• custom endpoints

[AngelliaX]

add it yourself man, then make a PR for us

[janbaykara]

I have achieved this through a local patch of the package. Feel free to take that and turn it into a PR: gameworkersolidarity/website@ebfb009