Adjust badges, bump SQLAlchemy test version and add "workflow_dispatch"

[amotl]

Hi there,

this is just a minor update which refreshes the badges displayed within README.rst. However, its main purpose was to investigate why CI tests would not run on #395.

• Adjust and add some badges to README.rst.
• For covering the most recent SQLAlchemy 1.3 release, bump CI to use SQLAlchemy version 1.3.23.
• Also, enable listening to workflow_dispatch events in order to be able to trigger workflows manually from the UI.

With kind regards,
Andreas.

[amotl]

to investigate why tests on GitHub Actions would not run?

-- https://discourse.julialang.org/t/compathelper-workflows-disabled-after-60-days-of-inactivity/48870

---

I pressed the button in order to re-enable that workflow again.

[seut]

👍

[amotl]

Its main purpose was to investigate why CI tests would not run on #395.
Enable listening to workflow_dispatch events in order to be able to trigger workflows manually from the UI.

Unfortunately, while this will enable us to invoke workflows from the UI on branches within this repository now, one can not invoke the workflow again on a pull request branch.

So, things like [1] might enable that feature through trigger commands as we know from Jenkins [2].

[1] https://github.com/marketplace/actions/pull-request-comment-trigger
[2] https://plugins.jenkins.io/github-pr-comment-build/