Adding checklists for the issue tracker

[fziegner]

This PR addresses #174 by adding templates for the issue tracker. I checked how projects like pandas and numpy manage this which mostly is in the form of interactive forms using YAML. These don't allow editing the issue while creating it so I opted to use Markdown in the style of the pull request template.

I created a repository here so you can check out how the templates look like in action. Is this what you had in mind @freemansw1? Unfortunately, Markdown doesn't support variables so you'd still have to manually replace the version number in the release template.

• [x] Have you followed our guidelines in CONTRIBUTING.md?
• [x] Have you self-reviewed your code and corrected any misspellings?
• [ ] Have you written documentation that is easy to understand?
• [x] Have you written descriptive commit messages?
• [ ] Have you added NumPy docstrings for newly added functions?
• [ ] Have you formatted your code using black?
• [ ] If you have introduced a new functionality, have you added adequate unit tests?
• [ ] Have all tests passed in your local clone?
• [ ] If you have introduced a new functionality, have you added an example notebook?
• [x] Have you kept your pull request small and limited so that it is easy to review?
• [x] Have the newest changes from this branch been merged?

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Comparison is base (f87ea1e) 55.75% compared to head (17392d0) 56.79%. Report is 127 commits behind head on RC_v1.5.x.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## RC_v1.5.x #358 +/- ## ============================================= + Coverage 55.75% 56.79% +1.03% ============================================= Files 15 20 +5 Lines 3316 3435 +119 ============================================= + Hits 1849 1951 +102 - Misses 1467 1484 +17 ``` | [Flag](https://app.codecov.io/gh/tobac-project/tobac/pull/358/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=tobac-project) | Coverage Δ | | |---|---|---| | [unittests](https://app.codecov.io/gh/tobac-project/tobac/pull/358/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=tobac-project) | `56.79% <ø> (+1.03%)` | :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=tobac-project#carryforward-flags-in-the-pull-request-comment) to find out more.

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[fziegner]

Thanks for the reviews. I'll remove the draft status then.

[freemansw1]

The notebook CI is failing, but it was also doing so before this PR. I've opened a new issue for that (#370). @fziegner are you happy for us to go ahead and merge this?

[w-k-jones]

I'm happy to merge as well, as the Jupyter CI issue has nothing to do with this PR

[fziegner]

Yes @freemansw1, no objections from me.