Asset globbing for `**/* should match root directory files

[danielrbradley]

Given the directory structure:

a.txt
subdir/b.txt

When using the glob **/*.txt I would expect to find both the a.txt and b.txt but we currently only return b.txt.

This is due to the globbing library in use treating the / as a required character, which a.txt doesn't have due to being in the root directory.

This is a simple example, but other related matches also have issues due to the same lack of collapsing **/ into **.