class SimpleWeightedCompletionMatcher

Calculates a weight value for each CompletionItem, and sorts by weight.

Filtering:

• Case-insensitive. Calls `toLowerCase() on all text.
• The first character of the filter text must match the first character of the CompletionItem text.
• The CompletionItem text must contain every character from the filter text, in order, but the characters don't need to be consecutive.

Sorting:

• Sorts by weight, ascending.
• A weight value of 0 is a perfect match.
• For every character in the CompletionItem text that is skipped, and for every remaining character after the filter text is exhausted, the weight increases by one.
• If two weight values match, falls back case-insensitive string comparison.