Add instructions on input data format

[RunzeZhang123]

Placeholder to add better instructions on the input data formatting.

[ma-sadeghi]

Hi @RunzeZhang123, here's what I think should be addressed in this PR:

• Explain what's required by AutoEIS as input
• Introduce pyimpspec package and list supported formats (check their documentation)
• Add an example of using pyimpspec to load EIS data from a proprietary data fromat and convert to the inputs required by AutoEIS (i.e., freq and complex impedance arrays)
• Bonus: Add a minimal example notebook for above (using pyimpsec) and put it under examples/ folder, so we can include it in our automated test suite (this way, we'll know if there's a breaking API change)

Preferably all in a single markdown file. Feel free to add more items if I missed anything.

[ma-sadeghi]

Nice work. Here are the things that would make the document more manageable:

• Make it a proper ipynb file, and the code snippet a proper python code cell
• Download 3 sample datasets from pyimpspec tests folder and actually load the data and visualize using autoeis to show users how to work with real data (data coming from real EIS devices)
• Dump the toy datasets into AutoEIS/src/assets and access it via utils.get_assets_folder()