Configuration schema is missing

Problem/Motivation

Configuration import failing due to missing configuration schema for show_logout_link.

Steps to reproduce

1. Make sure schema checker is enabled
2. Install module
3. Go to Structure -> Block layout (/admin/structure/block)
4. Click "Place block" in any region
5. Place "Login Form Popup" block
6. Click on "Save block"

Proposed resolution

Add configuration schema to the module.

Remaining tasks

None.

User interface changes

None.

API changes

None.

Data model changes

None.