readme-update-with-wiki

[jharenza]

rework the readme - reduce this page and refer users to the wiki where there are more detailed instructions.

Purpose/implementation Section

What feature is being added or bug is being addressed?

This PR updates the readme - moves longer documentation instructions to user guide Move custom input instructions to before cavatica

What was your approach?

What GitHub issue does your pull request address?

Directions for reviewers. Tell potential reviewers what kind of feedback you are soliciting.

Which areas should receive a particularly close look?

Is there anything that you want to discuss further?

Documentation Checklist

• [ ] The function has examples to showcase the usage
• [ ] Added a vignette

[jungkim2]

minor edits for me as well