Add issue templates

This adds two issue templates to speed up reporting and ease development.

.github/ISSUE_TEMPLATE/bug_report.md

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+---
+name: Bug report
+about: Create a report to help us improve
+title: "[BUG] "
+labels: ''
+assignees: ''
+
+---
+
+<!-- This template is there to guide you and help us. If you can not complete everything here, that is fine. -->
+## Describe the bug
+<!-- A clear and concise description of what the bug is. -->
+
+## To Reproduce
+<!-- Please add the neccesary code here to reproduce the problem on your machine. -->
+
+```
+import icalendar
+...
+```
+Output:
+<!-- If applicable, add logs or error outputs to help explain your problem. -->
+```
+
+```
+
+## Expected behavior**
+<!-- A clear and concise description of what you expected to happen. -->
+
+## Environment
+<!-- please complete the following information: -->
+ - [ ] OS:                               <!-- e.g. Ubuntu 22 or Windows 10 -->
+ - [ ] Python version:            <!-- e.g. Python 3.10 -->
+ - [ ] `icalendar` version:      <!-- python3 -c 'import icalendar; print(icalendar.__version__)' -->
+
+## Additional context
+<!-- Add any other context about the problem here, related issues and pull requests. -->
+- [ ] I tested it with the latest version `pip3 install https://github.com/collective/icalendar.git`
+- [ ] I attached the ICS source file or there is no ICS source file

.github/ISSUE_TEMPLATE/empty-issue.md

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+---
+name: empty issue
+about: This is an unstructured issue template to use with issues that are not described,
+  yet.
+title: ''
+labels: ''
+assignees: ''
+
+---
+
+<!-- This is an unstructured issue template to use if you do not need guidance.
+Here are some hints though:
+- add ICS example files if you can
+- show code if possible
+- show error output or output that differs from what you expect
+- it is nice to connect to the value of this issue
+Thanks for taking your time to report this!
+ -->