[Popper] Allow more control over avoidCollisions

[jgoz]

Ref #1568.

Description

Expands the possible values for avoidCollisions to include the following:

• auto — current behavior (as of 1.0.0) — Shift along the main axis and flip over the cross axis
• flip — Flip along both axes, but don't shift
• shift — Shift along the main axis only, but don't flip
• off — disable collision avoidance

Boolean values are still accepted for compatibility:

• true → auto
• false → off

I looked for Stories that would be appropriate to extend, but couldn't find any that demonstrated the shift+flip/auto behavior. Happy to add one if a maintainer pointed me in the right direction.

Open questions

• In shift mode, should we set crossAxis: true? Or should flip and shift act as strict behavioral subsets of auto, per the current implementation?

[andy-hook]

thanks @jgoz , I left a follow up regarding similar options and wanted to share that sentiment here 🙏

[jgoz]

Thanks @andy-hook! Feel free to close this PR to reduce noise. Looking forward to the solution you come up with