Cache Devicons Node:highlighted_name|icon

[alex-courtis]

Devicons HighlightedString for name and icon will not change unless:

• options change
• name changes

1. Cache these in the Node (preferred)
2. add a cache around get_icon (will grow large, avoid)

1 could be achieved by overloading .name.
It doesn't appear that name is set anywhere, hence safe to calculate once during construction.
Explorer will be destroyed on options change, clearing cached values.