[CORL-2979]: Add custom reason field to Other rejection reason

[kabeaty]

What does this PR do?

This adds a required Custom reason textbox to the rejection reason modal in the case that the Other reason is selected. This supports rejecting comments for custom reasons.

These changes will impact:

• [x] commenters
• [x] moderators
• [x] admins
• [ ] developers

What changes to the GraphQL/Database Schema does this PR introduce?

This adds the customReason field to RejectionReason to support this.

Does this PR introduce any new environment variables or feature flags?

no

If any indexes were added, were they added to INDEXES.md?

n/a

How do I test this PR?

You can go to a comment in the stream and reject it. Select the Other reason. See that there's now a required Custom reason field when Other is selected. Type a custom reason and click reject. See that the custom reason is saved. An additional explanation can also still be added. Other rejection reasons should still behave as before.

Also see that the same changes are reflected in the admin for rejection reason modal.

Where any tests migrated to React Testing Library?

How do we deploy this PR?

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