feat: Add re-usable components

[fsbraun]

When designing frontends it is key to avoid repeating template/HTML code. This PR makes djangocms-frontend components like alerts, cards, buttons or links, etc.

This PR provides a simple way to re-use djangocms-frontend plugins in templates:

{% load frontend %}
{% url "some-name" as link_target %}
{% plugin "link" external_link=link_target link_type="btn" link_context="primary" link_outline=False %}
    Click me!
{% endplugin %}

or

{% load frontend %}
{% plugin "card" card_alignment="center" card_outline="info"  card_text_color="primary" card_full_height=True %}
    {% plugin "cardinner" inner_type="card-header" text_alignment="start" %}
        <h4>Card title</h4>
    {% endplugin %}
    {% plugin "cardinner" inner_type="card-body" text_alignment="center" %}
        Some quick example text to build on the card title and make up the
        bulk of the card's content.
    {% endplugin %}
    {% plugin "listgroupitem" %}An item{% endplugin %}
    {% plugin "listgroupitem" %}A second item{% endplugin %}
    {% plugin "listgroupitem" %}A third item{% endplugin %}
{% endplugin %}

These plugins are not created in the database. They work with djangocms-frontend plugins and most other django CMS plugins.

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 80.83004% with 97 lines in your changes missing coverage. Please review.

Project coverage is 86.70%. Comparing base (f11feee) to head (effbde2). Report is 40 commits behind head on master.

Files with missing lines	Patch %	Lines
djangocms_frontend/contrib/link/helpers.py	48.14%	18 Missing and 10 partials :warning:
djangocms_frontend/templatetags/frontend.py	81.81%	11 Missing and 7 partials :warning:
djangocms_frontend/helpers.py	68.00%	9 Missing and 7 partials :warning:
djangocms_frontend/frameworks/tailwind.py	0.00%	13 Missing :warning:
djangocms_frontend/contrib/component/components.py	93.02%	2 Missing and 4 partials :warning:
...ms_frontend/contrib/icon/templatetags/icon_tags.py	37.50%	5 Missing :warning:
djangocms_frontend/contrib/component/registry.py	76.47%	2 Missing and 2 partials :warning:
djangocms_frontend/common/__init__.py	76.92%	3 Missing :warning:
djangocms_frontend/cms_plugins.py	90.47%	1 Missing and 1 partial :warning:
djangocms_frontend/component_pool.py	97.91%	0 Missing and 1 partial :warning:
... and 1 more

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #220 +/- ## ========================================== - Coverage 86.93% 86.70% -0.23% ========================================== Files 120 124 +4 Lines 3107 3422 +315 Branches 330 404 +74 ========================================== + Hits 2701 2967 +266 - Misses 304 333 +29 - Partials 102 122 +20 ```

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