make addon_before_class and addon_after_class effective

[phith0n]

addon_before_class and addon_after_class don't take effect as per its document:

        addon_before_class
            Class used on the span when ``addon_before`` is used.

            One of the following values:

                * ``'input-group-text'``
                * ``None``

            Set to None to disable the span inside the addon. (for use with buttons)

            :default: ``input-group-text``

        addon_after_class
            Class used on the span when ``addon_after`` is used.

            One of the following values:

                * ``'input-group-text'``
                * ``None``

            Set to None to disable the span inside the addon. (for use with buttons)

            :default: ``input-group-text``

So this PR added code for it.

[coveralls]

Pull Request Test Coverage Report for Build 2808049386

• 5 of 6 (83.33%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage decreased (-0.2%) to 96.902%

---

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
src/django_bootstrap5/renderers.py	5	6	83.33%
<!--	Total:	5	6

Totals
Change from base Build 2808047857:	-0.2%
Covered Lines:	587
Relevant Lines:	601

---

💛 - Coveralls

[dyve]

Thanks! Could you also add a unit test for this change?

[dyve]

Thanks, we had 2 PR's for this one it seems. This was fixed in #361

[phith0n]

Thanks, we had 2 PR's for this one it seems. This was fixed in #361

Good job, thanks~