fix(element-template): add asyncBefore and asyncAfter property

[peterhnm]

• add complex parameter to the maven plugin
• add asyncBefore and asyncAfter property to the generated element-template
• update tests
• update README.md

closes #414

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 93.87755% with 3 lines in your changes missing coverage. Please review.

Project coverage is 46.98%. Comparing base (fb10ad3) to head (aed1504). Report is 1 commits behind head on main.

Files	Patch %	Lines
.../elementtemplate/ElementTemplateGeneratorMojo.java	88.23%	2 Missing :warning:
...menttemplate/ElementTemplateGeneratorsFactory.java	50.00%	1 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #414 +/- ## ============================================ + Coverage 46.06% 46.98% +0.91% - Complexity 397 407 +10 ============================================ Files 187 189 +2 Lines 2086 2122 +36 Branches 110 111 +1 ============================================ + Hits 961 997 +36 Misses 1091 1091 Partials 34 34 ``` | [Flag](https://app.codecov.io/gh/Miragon/miranum/pull/414/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Miragon) | Coverage Δ | | |---|---|---| | [unittests](https://app.codecov.io/gh/Miragon/miranum/pull/414/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Miragon) | `46.98% <93.87%> (+0.91%)` | :arrow_up: | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Miragon#carryforward-flags-in-the-pull-request-comment) to find out more.

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[peterhnm]

@DaAnda97 Yes for me the boolean value works. Also when I unlink the element template the value is set correctly.

[DaAnda97]

you're right. I added the feature to our example project and confirmed that everything works! Great job. Thank you!