Add missing gradient before on notification item

Editor assessment

'Gradient before' presumably means a before-pseudo-element gradient, but the compressed phrasing makes the reader guess at the CSS anatomy, and no scope or body resolves the ambiguity. Fix is a plausible type for a missing visual, though style could fit equally. There is no body, and a visual bug fix is exactly where a sentence describing the broken appearance would help reviewers and future archaeologists; none is offered. Hygiene is otherwise acceptable: imperative, no trailing period, no junk. Ultimately decipherable and valid, but too compressed to teach anything about the defect or the remedy.