SCOPING: Add mobile device support

## Summary

Researchers have been asking about running studies on mobile devices, and some participants may prefer to access CHS on these devices. While CHS is somewhat mobile-compatible, we should consider improving mobile device support, and introducing features to facilitate this.

Related issues: #164

## Website

- [ ] Go through all family-facing pages and workflows to identify any issues on phones/tablets. Any issues should be moved into separate issues and marked as either priority/critical (broken functionality) or not (e.g. minor formatting). #1219
- [ ] Introduce a new 'device compatibility' multi-select field to the Study form, so that researchers can mark their studies as being mobile compatible. Options could be (1) laptop/desktop (default selection), (2) tablets, (3) mobile phones. These would not be mutually exclusive. #1528
- [ ] Detect the user's device type and add banner messages and/or eligibility warnings related to their device's compatibility with studies (in general, and for the specific study on the participation page). Adding this as an eligibility type requires adding a new eligibility value "ineligible_device" and updating our eligibility checks.
- [ ] Add view tests for mobile compatibility.

## Experiment runners

These sub-issues should be created in the EFP and jsPsych repositories.

- [ ] Go through frame/trial types that should be mobile-compatible and identify any issues on phones/tablets. Any issues should be moved into the appropriate repo and marked as either priority/critical (broken functionality) or not (e.g. minor formatting). https://github.com/lookit/lookit-jspsych/issues/64
- [ ] In the documentation, identify the frame/trial types that are/aren't mobile-compatible.
- [ ] Record device type in the response data.
- [ ] If device type detection is unreliable, add a method for handling this (e.g. confirmation from participant at the start).
- [ ] Add view tests for mobile compatibility.