Add move domain for repositioning items

[gus-costa]

Implements the --move domain to allow repositioning items relative to other items in SketchyBar.

Related to #11

API

Item method:

item:move("before", reference_item)
item:move("after", reference_item)

Module function:

sbar.move("item_name", "before", "reference_name")

Changes

• Added move() function in src/sketchybar.c following existing domain patterns
• Supports both item table references and string names for flexibility
• Updated README.md with Move Domain documentation and examples
• Added Lua build artifacts to .gitignore

Example

local calendar = sbar.add("item", "calendar", { label = "📅" })
local clock = sbar.add("item", "clock", { label = "🕐" })

-- Move calendar to appear after clock
calendar:move("after", clock)

Maps to SketchyBar CLI: sketchybar --move <name> before/after <reference>