Versioning for template.json schema

[vlada-shubina]

Consider establishing the versioning schema for template.json schemas:

• all previous version to use current schema - template
• n+1 version: template.json should be versioned as template-<version number>, example: template-9.0.200
• in case there is no changes to schema in certain version, the version is skipped.

Subtasks:

• release new version of template-<version number> schema to schemastore.org
• document schema versioning
• Implement check for schema version when running the template (based on $schema) - in case template version is higher than dotnet version, raise a warning (can be done via validation Authoring tools: templates & template packages validation #2623)