Issue 5177: Allow colors to be changed using Up/Down keys

Steps to reproduce

  1. Inspect the blue <div> above.
  2. Switch to the Style side panel.
  3. Click on the value of the background property to start inline editing.
  4. Enter a value of "#9af ", and press up/down randomly with different selections.
    ⇒ The value and selection should match current behavior
  5. Enter the following values, press up/down randomly with the cursor at random positions, and verify that the resulting value and selection matches current behavior:
    • "#9af "
    • "rgba(1,3, 9,0)"
    • "hsla(3,30%,9%,0"

Expected Results