feat: add template registry for handling template files

[travbale]

This change creates a TemplateRegistry type for managing the collection of template objects and operations related to templates. The biggest change is related to using Go's embed package to embed all ignore templates into the compiled binary. This has the benefit of not needing to read from the file system or scrape the Go module cache for the templates directory.

• Moved templates to internal/ignore/templates to allow for embedding it's contents in the ignore package.
• Created ignore.TemplateRegistry with HasTemplate, List, and CopyTemplate operations.
• Adjusted relevant commands to utilize ignore.TemplateRegistry.
• Added test cases for ignore.TemplateRegistry.