Properly support / in filter queries

[abey79]

We discussed a plan with @Wumpf.

The plan is:

• parse the input query into keyword as below.
• update match logic accordingly
• for the highlight ranges:
  • perform ranges extraction for the full hierarchy in leaf items
  • accumulate (HashSet?) match ranges in the hierarchy vector
  • merge ranges after traversing children, based on hierarchy.last()

enum Keyword {
        parts: Vec<&str>,

		/// e.g. if the query is "/a/b/c"
        first_part_must_fully_match: bool,

	    /// e.g. if the query is "a/b/c/"
        last_part_must_fully_match: bool,
}