fix: Add missing sample app paths to oathkeeper config

[theotherian]

Add "welcome,registration,login,verification" and "**.png" to the paths oathkeeper forwards to self service ui.

Currently the self service UI doesn't work when using quickstart-oathkeeper.yml from https://www.ory.sh/kratos/docs/guides/zero-trust-iap-proxy-identity-access-proxy/. This is due to the paths above missing from the access rules.

Related issue(s)

Fixes #2048

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[aeneasr]

Thank you so much!