node selection for Package Dependencies should ignore case when sorting dropdown

[jameslamb]

I noticed tonight that the Dependency Network dropdown looks like this:

The sort order is:

• All packages starting with a capital letter (sorted alphabetically)
• All packages starting with a lowercase letter (sorted alphabetically)

I think people often ignore case mentally when thinking about R packages. In the screenshot above, I scrolled down further than what is shown looking for HistogramTools in the "h" section and then was surprised to find that it's near the top of the list because it starts with a capital letter.