feat: add option to customize template in custom admin views config

[r1tsuu]

Description

Currently a custom views in beta are wrapped with the Minimal template by default and you can't remove it and neither change it to the Default template. Because of this i can't migrate the views in my application from 2.0 to 3.0 (in 2.0 we were importing templates directly, but i guess this way could be better as less boilerplate) Adds also abillity to apply classname to the template Included e2e change requires to update the doc but currently the doc mentions react-router so i think it's not updated to beta at this point.

• [x] I have read and understand the CONTRIBUTING.md document in this repository.

Type of change

• [x] New feature (non-breaking change which adds functionality)
• [x] This change requires a documentation update

Checklist:

• [x] I have added tests that prove my fix is effective or that my feature works
• [x] Existing test suite passes locally with my changes

[r1tsuu]

this is the only thing why i'm using a custom version of Payload now (will consider patching probably because i'm tired of maintaing monorepo) you clearly cannot migrate a custom view that uses default template from 2.0 to 3.0 without this change (or custom next js page, which could be awkward) or i'm missing something?