If you’re developing a Kirby plugin to share it with the Kirby community, it’s probably not a great idea to make it rely on kirby-twig. You should probably provide PHP templates or snippets.
For project-specific plugins, though, if your project is using Twig, you might want to keep your plugin-related templates and snippets in your plugin’s folder. Here are a few config tricks that might help.
<?php
// site/myplugin/myplugin.php
/**
* Add a Twig namespace for our plugin's templates
* Allows including with {% include '@myplugin/mytemplate.twig' %}
*/
c::set('twig.namespace.myplugin', __DIR__ . '/templates');
/**
* Expose functions from our plugin to the Twig environment
*/
$twigFunctionNames = array_merge(
c::get('twig.env.functions', []),
['myPluginFunction', 'myOtherFunction']
);
c::set('twig.env.functions', $twigFunctionNames);
See Using your own functions in templates for more details about exposing functions, static methods and classes to templates.