Add dependabot to manage Github Actions update

[woodsp-ibm]

Summary

Build have started emitting warnings:

Node.js 16 actions are deprecated. Please update the following actions to use Node.js 20: actions/checkout@v3, actions/setup-python@v4, actions/cache@v3, actions/upload-artifact@v3. For more information see: https://github.blog/changelog/2023-09-22-github-actions-transitioning-from-node-16-to-node-20/.

I recently fixed these manually in qiskit algorithms but then saw qiskit experiments setup dependabot to check and update the actions. Upon finding actions needing update it will create a PR for this. So this is a first step to setting that up and commits a config file for dependabot to use, once that's in place there are other settings to enable it etc that I will do so once this merged. It seems better to have this automated.

Details and comments

In doing this first on Qiskit Machine Learning it seems that dependabot will do a PR for each action it updates. This meant separate PRs for the change in version to the upload-artifact and download-artifact, This is seemed would cause a failure in each of the PRs that I surmise is due to the upload being done in one version and the download with another. The download would always fail saying file could not be found. In ML I fixed things by doing a manual PR that did both at the same time hence #1317.

I marked this OnHold since it would be better to merge this after #1317 is merged. And while I could have updated all the actions manually I figured not doing so would allow us to check dependabot is working ok for Nature here

[coveralls]

Pull Request Test Coverage Report for Build 7741308121

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 1 unchanged line in 1 file lost coverage.
• Overall coverage increased (+0.009%) to 86.765%

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Files with Coverage Reduction	New Missed Lines	%
qiskit_nature/second_q/drivers/psi4d/psi4driver.py	1	85.12%

Totals
Change from base Build 7741299066:	0.009%
Covered Lines:	8785
Relevant Lines:	10125

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💛 - Coveralls