Add support for emoji definitions in bounty label

The tool to automatically put a bounty label on issues works well. However, when you try to add a emoji such as `:moneybag:` it fails to apply. :moneybag:

Start by locating the tool that automatically applies the bounty label and reproduce the failure with the `:moneybag:` definition. Trace how the label value is handled, then verify that an emoji definition is accepted and the bounty label is applied successfully.

Written by the indexing model from the issue text.