Improve selection highlighting

[supersaiyansubtlety]

based on #317

Makes several improvements to the blinking outline that indicates which entry has been navigated to:

• stops any previous blinking on other entries
• removes initial delay
• makes the number of blinks and the delay configurable (set blinks to 0 to disable)
• when opening a class, waits for it to fully load before highlighting its first entry

Before

selection-highlighter-before.mp4

After

selection-highlighter-after.mp4

Custom

# Settings for the editor's selection highlighting; used to highlight tokens that have been navigated to.
# The color of the highlight is defined per-theme (in themes/) by [syntax_pane_colors] -> selection_highlight.
[selection_highlight]
	# The number of times the highlighting blinks. Set to 0 to disable highlighting.
	# default: 3 (min: 0, max: 10)
	blinks = 2
	# The number of milliseconds the highlighting should be on and then off when blinking.
	# default: 200 (min: 10, max: 5000)
	blink_delay = 150

selection-highlighter-custom.mp4