Add missing config schema definitions for X-XSS-Protection options in Seckit

Problem/Motivation

The Seckit module defines several X-XSS-Protection option keys in its configuration, but these keys are currently missing from the module’s config schema.

Specifically, the following settings are present in configuration and used by the module, but are not declared in seckit.schema.yml:

seckit_x_xss_option_disable

seckit_x_xss_option_0

seckit_x_xss_option_1

seckit_x_xss_option_1_block

Because these keys are not defined in the schema, tools like Config Inspector report schema validation warnings for otherwise valid Seckit configuration.

Steps to reproduce

1. Install and enable the Seckit module.
2. Ensure Seckit configuration includes X-XSS-Protection options (default or customized).
3. Run a configuration schema validation tool, for example:
4. Navigate to Reports → Configuration inspector
5. Inspect seckit.settings
6. Observe schema validation warnings for the following keys:
   1. seckit_x_xss_option_disable
   2. seckit_x_xss_option_0
   3. seckit_x_xss_option_1
   4. seckit_x_xss_option_1_block

Proposed resolution

Apply patch that adds explicit schema definitions for the missing X-XSS-Protection option keys under seckit.settings, aligning the schema with the actual configuration used by the module.

Why this matters

Eliminates false-positive schema warnings

Improves configuration correctness and introspection

Keeps Seckit compliant with Drupal’s configuration schema best practices

No functional behavior changes — schema only

Remaining tasks

Review the patch.

User interface changes

API changes

Data model changes